Polishing apparatus

ABSTRACT

A polishing apparatus is used for polishing a workpiece such as a semiconductor wafer to a flat mirror finish. The polishing apparatus comprises a turntable having a polishing surface, a top ring for holding a workpiece and pressing the workpiece against the polishing surface to polish the workpiece, at least three cleaning apparatuses for cleaning polished workpieces, and a transfer structure for transferring the polished workpieces between at least three cleaning apparatuses. The polishing apparatus further includes a rotary transporter disposed in a position which can be accessed by said top rings and having a plurality of portions positioned on a predetermined circumference from a center of rotation of the rotary transporter for holding the workpieces.

This is a Divisional application of Ser. No. 10/026,763, filed Dec. 27,2001 now U.S. Pat. No. 6,682,408 which is a Divisional application ofSer. No. 09/663,417, filed Sep. 15, 2000, now U.S. Pat. No. 6,358,128,which is a continuation-in-part of application Ser. No. 09/518,958,filed Mar. 3, 2000 now abandoned, which is a continuation-in-part ofapplication Ser. No. 09/476,905 filed Jan. 3, 2000 now U.S. Pat. No.6,354,922.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus for polishing aworkpiece such as a semiconductor wafer to a flat mirror finish, andmore particularly to a polishing apparatus having a cleaning apparatusfor cleaning a polished workpiece and/or a transporter such as a rotarytransporter or a linear transporter for supplying workpieces.

2. Description of the Related Art

In semiconductor device manufacturing processes, semiconductor wafersare polished to a flat mirror finish in a semiconductor waferfabrication process, and layers formed on semiconductor devices arepolished to a flat mirror finish in a semiconductor device fabricationprocess. These polishing processes in the semiconductor waferfabrication process and the semiconductor device fabrication process areperformed by a polishing apparatus.

Conventionally, such a polishing apparatus has been designed as adedicated polishing apparatus having a single function of polishingsemiconductor wafers. The semiconductor wafers which have been polishedby the polishing apparatus are transported to a next cleaning process bya movable container in which they are immersed in water to keep themfrom drying during transportation. However, the cleaning process tendsto impair the cleanliness of a clean room, and the polishedsemiconductor wafers need to be transported by an operator or a manuallyoperated transportation means. Further, a large installation space isrequired for two kinds of apparatuses comprising the polishing apparatusand a cleaning apparatus that is used to carry out the subsequentcleaning process.

In an effort to make the polishing process clean and reduce theinstallation space of the apparatus, there has been developed apolishing apparatus which performs both a polishing process and acleaning process and which is of a dry-in and dry-out type forintroducing semiconductor wafers therein in a dry condition and removingpolished and cleaned semiconductor wafers therefrom in a dry condition.

On the other hand, the polishing apparatus having a single function ofpolishing semiconductor wafers has been improved to allow thecleanliness of a clean room to be maintained, and the polishingapparatus and the cleaning apparatus used in a cleaning process afterpolishing have an increased processing capability for thereby reducingthe number of the polishing apparatuses used for polishing processes andthe number of the cleaning apparatuses. As a result, the conventionaldedicated polishing apparatus having a single function of polishingsemiconductor wafers can reduce an installation space thereof to adegree which is equal to or smaller than the dry-in and dry-out typepolishing apparatus.

However, in the dedicated polishing apparatus having a single functionof polishing semiconductor wafers, the semiconductor wafers which havebeen polished by the polishing apparatus are transported still by anoperator or a manually operated transportation means, as before. If thetransportation means is automated, then it is difficult to handle thesemiconductor wafers because the semiconductor wafers are stored in themovable water tank. Thus, the problems are presented by thetransportation means in the conventional dedicated polishing apparatus.

Further, the dry-in and dry-out type polishing apparatus has aprocessing capability per unit time and unit installation area lowerthan the conventional dedicated polishing apparatus having a singlefunction of polishing the semiconductor wafers. Thus, the number ofapparatuses in the polishing processes is large, and a largeinstallation space is required, and the running cost of the apparatusesis high.

The dry-in and dry-out type polishing apparatus has two cleaningapparatuses operable based on two different cleaning methods forcleaning semiconductor wafers which have been polished, in order toincrease the processing capability per unit installation area. Such twocleaning apparatuses clean a semiconductor wafer in two stages, and areinstalled in a smaller installation area with minimum cleaningfunctions. However, as recent semiconductor devices have smaller circuitelements and finer interconnections in integrated patterns, there hasbeen a demand for removing polished semiconductor wafers from thepolishing apparatus in a higher level of cleanness, and therefore thecleaning stages for cleaning the polished semiconductor wafers haveincreased from two stages to three stages to meet such a demand.Specifically, such three cleaning stages include a process of removingfine particles attached to the polished semiconductor wafer, a processof removing metal ions attached to the polished semiconductor wafer, anda process of drying the clean polished semiconductor wafer. In somecases, two or more types of metal ions attached to the polishedsemiconductor wafer are removed by different chemicals supplied thereto,with the result that a total of four stages are involved in cleaning thepolished semiconductor wafer. The four cleaning stages may be performedby respective four cleaning apparatuses, or two stages of the fourcleaning stages may be performed by one of three cleaning apparatuses.

If three or more cleaning stages are carried out by two cleaningapparatuses, then two cleaning stages are performed by at least onecleaning apparatus, whose processing capability is thus reduced per unittime. If three or more cleaning apparatuses are provided in a row in apolishing apparatus, then the polishing apparatus becomes large in size,and has a reduced processing capability per unit time.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide apolishing apparatus which can be used as a dry-in and dry-out typepolishing apparatus, has a high processing capability per unit time andunit installation area for processing workpieces such as semiconductorwafers, has three or more cleaning stages in a cleaning process, and iscapable of making semiconductor wafers cleaner to meet requirements forsmaller circuit elements and finer interconnections on semiconductordevices.

Further object of the present invention is to provide a polishingapparatus which can be used as the dry-in and dry-out type polishingapparatus and is capable of greatly increasing a processing capabilityof workpieces such as semiconductor wafers per unit time and unit area.

To achieve the above objects, according to a first aspect of the presentinvention, there is provided a polishing apparatus comprising: aturntable having a polishing surface; a top ring for holding a workpieceand pressing the workpiece against the polishing surface to polish theworkpiece; at least three cleaning apparatuses for cleaning polishedworkpieces; and a transfer structure for transferring the polishedworkpieces between the at least three cleaning apparatuses, the transferstructure being capable of changing transfer routes between the at leastthree cleaning apparatuses. The transfer structure comprises a pluralityof robots.

According to the present invention, the polishing apparatus can changetransfer routes to comply with the required cleaning processes formaintaining a desired number of cleaning stages depending on variouspolishing processes without reducing the processing capability per unitinstallation area, and also to shorten the processing time of each ofthe cleaning processes by assigning the cleaning process which needs along period of time to at least two cleaning apparatuses, for therebyincreasing the number of processed workpieces per unit time, i.e.,throughput.

According to a second aspect of the present invention, there is provideda polishing apparatus comprising: a plurality of turntables havingrespective polishing surfaces; a plurality of top rings for holdingworkpieces and pressing the workpieces against the polishing surfaces topolish the workpieces; a rotary transporter disposed in a position whichcan be accessed by the top rings and having a plurality of portionspositioned on a predetermined circumference from a center of rotation ofthe rotary transporter for holding the workpieces, the rotarytransporter being capable of replacing the workpieces placed at theportions; a pusher for transferring the workpieces between the rotarytransporter and the top rings; and a reversing device for transferringthe workpieces to and from the rotary transporter and reversing theworkpieces.

It is possible to shorten the time required to transfer a workpiece tobe polished, such as a semiconductor wafer, to the top ring, for therebygreatly increasing the number of processed workpieces per unit time,i.e., throughput.

According to a third aspect of the present invention, there is provideda polishing apparatus comprising: a polishing section for polishing aworkpiece; a cleaning section for cleaning a polished workpiece; and areversing device for reversing a workpiece to be polished and a polishedworkpiece; the polishing section being arranged to polish a workpiecewhile a surface thereof being polished is directed downwardly, and thecleaning section being arranged to clean said polished workpiece while apolished surface thereof is directed upwardly.

In the cleaning processes, the polished surfaces of workpieces can beprocessed while the polished surfaces are being directed upwardly.

According to a fourth aspect of the present invention, there is provideda polishing apparatus comprising: a turntable having a polishingsurface; a top ring for holding a workpiece and pressing the workpieceagainst the polishing surface to polish the workpiece; a plurality ofcleaning apparatuses for cleaning polished workpieces; and a workpiecestation having workpiece supports for holding workpieces in a standbystate while the workpieces are cleaned in a plurality of stages throughthe cleaning apparatuses.

Inasmuch as polished workpieces can wait while being processed incleaning processes, a plurality of cleaning processes having differentprocessing times can be performed parallel to each other on a pluralityof polished workpieces.

According to a fifth aspect of the present invention, there is provideda polishing apparatus comprising: a loading and unloading section forsupplying a workpiece to be polished and receiving a polished workpiece;a polishing section for polishing the workpiece; and a cleaning sectionfor cleaning the polished workpiece; and chambers separated bypartitions having respective openings for allowing the workpiece to passtherethrough, the loading and unloading section, the polishing section,and the cleaning section being housed in the chambers.

Since the chambers in which cleanliness of atmosphere is different fromone another are separated by the partitions, the atmosphere in acontaminated chamber is prevented from flowing into a clean chamber andhence from lowering the cleanliness in the clean chamber.

According to a sixth aspect of the present invention, there is provideda polishing apparatus comprising: a plurality of turntables havingrespective polishing surfaces; a plurality of top rings for holdingworkpieces and pressing the workpieces against the polishing surfaces topolish the workpieces; a plurality of cleaning apparatuses for cleaningpolished workpieces; and a transfer structure for transferring theworkpieces; the polishing surfaces including a polishing surface forprimarily polishing the workpiece and a polishing surface for finishpolishing the workpiece.

The polishing surface for polishing the workpiece to produce a polishedsurface at a higher polishing rate and the polishing surface forpolishing the workpiece to produce a finer polished surface in thefinish manner at a lower polishing rate are combined with each other toefficiently polish the workpiece to produce a well polished surfacethereof.

According to a seventh aspect of the present invention, there isprovided a polishing apparatus comprising: a loading and unloadingsection for supplying a workpiece to be polished and receiving apolished workpiece; a turntable having a polishing surface; a top ringfor holding a workpiece and pressing the workpiece against the polishingsurface to polish the workpiece; at least three cleaning apparatuses forcleaning polished workpieces, at least two of the three cleaningapparatuses having an identical cleaning function; and a transferstructure for transferring the workpieces.

Of the three cleaning apparatuses, at least two of the cleaningapparatuses have identical cleaning modules. Consequently, cleaningprocesses which need to be performed in a long period of time can becarried out by two or more cleaning apparatuses, i.e., a tact time canbe distributed, to increase the number of processed workpieces per unittime, i.e., throughput.

According to an eighth aspect of the present invention, there isprovided a polishing apparatus comprising: a plurality of turntableshaving respective polishing surfaces; a plurality of top rings forholding workpieces and pressing the workpieces against the polishingsurfaces to polish the workpieces; a rotary transporter disposed in aposition which can be accessed by the top rings and having a pluralityof portions positioned on a predetermined circumference from a center ofrotation of the rotary transporter for holding the workpieces, therotary transporter being capable of indexing the plurality of portions;and a pusher for transferring the workpieces between the rotarytransporter and the top rings.

According to a ninth aspect of the present invention, there is provideda polishing apparatus comprising: a plurality of turntables havingrespective polishing surfaces; a plurality of top rings for holdingworkpieces and pressing the workpieces against the polishing surfaces topolish the workpieces; a plurality of rotary transporters provided so asto correspond to the respective top rings and disposed in positionswhich can be accessed by the respective top rings and each having aplurality of portions positioned on a predetermined circumference from acenter of rotation of the rotary transporter for holding the workpieces,the rotary transporter being capable of indexing the plurality ofportions; and a pusher for transferring the workpieces between therotary transporter and the top rings.

According to a tenth aspect of the present invention, there is provideda polishing apparatus comprising: a plurality of turntables havingrespective polishing surfaces; a plurality of top rings for holdingworkpieces and pressing the workpieces against the polishing surfaces topolish the workpieces; a rotary transporter having an indexing functionfor transferring the workpieces to or from the top rings; wherein eachof the plurality of top rings is angularly movable about a rotatingshaft to a position over the turntable and a position over the indextable.

According to the eighth through tenth aspects of the present invention,it is possible to shorten the time required to transfer a workpiece tobe polished, such as a semiconductor wafer, to the top ring, for therebygreatly increasing the number of processed workpieces per unit time,i.e., throughput.

In a preferred embodiment, each of the top rings is angularly movableabout a rotating shaft to a position over one of the turntables and aposition over the rotary transporter.

In a preferred embodiment, respective dedicated dressers associated withthe respective turntables are provided.

In a preferred embodiment, the portions of the rotary transportercomprises a load stage for holding the workpiece to be polished and anunload stage for holding the workpiece which has been polished.

In a preferred embodiment, the pusher is provided below or on the rotarytransporter.

According to an eleventh aspect of the present invention, there isprovided a polishing apparatus comprising: a turntable having apolishing surface; a top ring for holding a workpiece and pressing theworkpiece against the polishing surface to polish the workpiece; atransporter having a plurality of movable stages for holding theworkpieces; a pusher for transferring the workpiece between the stageand the top ring; and a reversing device for transferring the workpiecebetween the stage and the reversing device, and reversing the workpiece.

According to the eleventh aspect of the present invention, it ispossible to shorten the time required to transfer a workpiece to bepolished, such as a semiconductor wafer, to the top ring, for therebygreatly increasing the number of processed workpieces per unit time,i.e., throughput.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a layout of various components of apolishing apparatus according to a first embodiment of the presentinvention;

FIG. 2 is an elevational view showing the relationship between a topring and turntables;

FIG. 3 is a diagram illustrative of a process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 4 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 5 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 6 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 7 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 8 is a diagram illustrative of another process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 9 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 10 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 11 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 12 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 13 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 14 is a diagram illustrative of the other process of polishing asemiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 15 is a diagram illustrative of still another process of polishinga semiconductor wafer with the polishing apparatus shown in FIG. 1;

FIG. 16 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 17 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 18 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 19 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 20 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 21 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIG. 22 is a diagram illustrative of the still other process ofpolishing a semiconductor wafer with the polishing apparatus shown inFIG. 1;

FIGS. 23A and 23B are front and side elevational views of a loading andunloading section;

FIG. 24 is a front elevational view of another loading and unloadingsection;

FIG. 25 is a schematic diagram showing air flows in a cleaning chamber;

FIG. 26 is a side elevational view of a transfer robot;

FIG. 27 is a perspective view of the transfer robot;

FIG. 28A is a front elevational view of a wafer station;

FIG. 28B is a side elevational view of the wafer station;

FIG. 28C is a view of the wafer station as viewed in the directionindicated by the arrow I;

FIG. 28D is a view of the wafer station as viewed in the directionindicated by the arrow II;

FIG. 28E is a view of the wafer station as viewed in the directionindicated by the arrow III;

FIG. 29A is a plan view of a reversing device;

FIG. 29B is a side elevational view, partly in cross section, of thereversing device;

FIG. 30 is a vertical cross-sectional view of a lifter;

FIG. 31 is a plan view of a rotary transporter;

FIG. 32 is a side elevational view of the rotary transporter;

FIG. 33 is a vertical cross-sectional view of a pusher;

FIGS. 34A through 34E are vertical cross-sectional views illustrative ofthe manner in which the pusher operates;

FIG. 35 is a side elevational view, partly in cross section, of a topring;

FIG. 36 is a vertical cross-sectional view of a diamond dresser;

FIG. 37 is a vertical cross-sectional view of a brush dresser;

FIG. 38 is a vertical cross-sectional view of a dresser of a secondturntable;

FIG. 39 is a side elevational view of the dresser of the secondturntable;

FIG. 40 is a front elevational view of a rotary-type turntable;

FIG. 41 is a vertical cross-sectional view of a scroll-type turntable;

FIG. 42A is a cross-sectional view taken along line P—P of FIG. 41;

FIG. 42B is a cross-sectional view taken along line X—X of FIG. 42A;

FIG. 43 is a vertical cross-sectional view of an overhanging-typeturntable;

FIG. 44A is a plan view of an abrasive liquid supply nozzle;

FIG. 44B is a side elevational view, partly in cross section, of theabrasive liquid supply nozzle;

FIG. 45 is a plan view showing the position of the abrasive liquidsupply nozzle with respect to a turntable;

FIG. 46 is a schematic diagram showing an abrasive liquid supply system;

FIG. 47 is a schematic diagram showing another abrasive liquid supplysystem; and

FIG. 48 is a schematic diagram showing still another abrasive liquidsupply system.

FIG. 49 is a plan view showing a layout of various components of apolishing apparatus according to a second embodiment of the presentinvention;

FIG. 50 is an elevational view showing the relationship between a topring and a turntable;

FIG. 51 is a plan view showing a detailed structure of a rotarytransporter type A;

FIG. 52 is an elevational view showing the detailed structure of therotary transporter type A;

FIG. 53 is a plan view showing a detailed structure of a rotarytransporter type B;

FIG. 54 is an elevational view showing the detailed structure of therotary transporter type B;

FIG. 55 is a plan view showing a detailed structure of a linearlymovable table type;

FIG. 56 is an elevational view showing the detailed structure of thelinearly movable table type;

FIG. 57 is a plan view the relationship of top rings, a rotarytransporter, pushers and transfer robots;

FIGS. 58A through 58D are vertical cross-sectional views showing themanner in which the pusher is operated;

FIG. 59 is a plan view showing a modified embodiment of the polishingapparatus shown in FIG. 49 according to the present invention;

FIG. 60 is a diagram illustrative of a process of polishing asemiconductor wafer with the polishing apparatuses shown in FIGS. 49 and59;

FIG. 61 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatuses shown in FIGS. 49 and59;

FIG. 62 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatuses shown in FIGS. 49 and59;

FIG. 63 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatuses shown in FIGS. 49 and59;

FIG. 64 is a diagram illustrative of the process of polishing asemiconductor wafer with the polishing apparatuses shown in FIGS. 49 and59;

FIG. 65 is a plan view showing a layout of various components of apolishing apparatus according to a third embodiment of the presentinvention;

FIG. 66 is an elevational view showing the relationship of a top ring, aturntable and a pusher unit;

FIG. 67 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 68 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 69 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 70 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 71 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 72 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 73 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 74 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 75 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 76 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 77 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 78 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 79 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 80 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 81 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 82 is a diagram illustrative of operation of the rotary transporteraccording to another embodiment;

FIG. 83 is a plan view showing a layout of various components of apolishing apparatus according to a fourth embodiment of the presentinvention;

FIG. 84 is a perspective view showing the polishing apparatus shown inFIG. 83;

FIG. 85 is an elevational view showing the relationship between a topring and turntables;

FIG. 86 is a perspective view showing the linear transporter, the lifterand the pusher;

FIG. 87A is a perspective view showing the air cylinder;

FIG. 87B is a plan view with partially cross-section showing anessential part of FIG. 87A;

FIG. 88A is a plan view showing the entire structure of the lineartransporter;

FIG. 88B is a view as viewed from an arrow A of FIG. 88A showing theentire structure of the linear transporter;

FIG. 88C is a view as viewed from an arrow B of FIG. 88A showing theentire structure of the linear transporter;

FIG. 89 is a perspective view showing the linear transporter as shown inFIG. 88; and

FIG. 90 is a schematic view showing transfer operation of asemiconductor wafer between the reversing device and the lineartransporter, and between the linear transporter and the top ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing apparatus according to embodiments of the present inventionwill be described below with reference to drawings.

FIG. 1 shows a layout of various components of a polishing apparatusaccording to a first embodiment of the present invention. As shown inFIG. 1, a polishing apparatus according to the present inventioncomprises four load-unload stages 2 each for placing a wafer cassette 1which accommodates a plurality of semiconductor wafers. The load-unloadstage 2 may have a mechanism for raising and lowering the wafer cassette1. A transfer robot 4 having two hands is provided on rails 3 so thatthe transfer robot 4 can move along the rails 3 and access therespective wafer cassettes 1 on the respective load-unload stages 2.

The transfer robot 4 has two hands which are located in a verticallyspaced relationship, and the lower hand is used only for taking out asemiconductor wafer from the wafer cassette 1 and the upper hand is usedonly for returning the semiconductor wafer to the wafer cassette 1. Thisarrangement allows that a clean semiconductor wafer which has beencleaned is placed at an upper side and is not contaminated. The lowerhand is a vacuum attraction-type hand for holding a semiconductor waferunder vacuum, and the upper hand is a recess support-type hand forsupporting a peripheral edge of a semiconductor wafer by a recess formedon the hand. The vacuum attraction-type hand can hold a semiconductorwafer and transport the semiconductor wafer even if the semiconductorwafer is not located at a normal position in the wafer cassette due to aslight displacement, and the recess support-type hand can transport asemiconductor wafer while keeping the semiconductor wafer clean becausedust is not collected unlike the vacuum attraction-type hand.

Two cleaning apparatuses 5 and 6 are disposed at the opposite side ofthe wafer cassettes 1 with respect to the rails 3 of the transfer robot4. The cleaning apparatuses 5 and 6 are disposed at positions that canbe accessed by the hands of the transfer robot 4. Between the twocleaning apparatuses 5 and 6 and at a position that can be accessed bythe transfer robot 4, there is provided a wafer station 50 having fourwafer supports 7, 8, 9 and 10. The cleaning apparatuses 5 and 6 have aspin-dry mechanism for drying a semiconductor wafer by spinning thesemiconductor wafer at a high speed, and hence the two-stage cleaning orthree-stage cleaning of the semiconductor wafer can be conducted withoutreplacing any cleaning module.

An area B in which the cleaning apparatuses 5 and 6 and the waferstation 50 having the wafer supports 7, 8, 9 and 10 are disposed and anarea A in which the wafer cassettes 1 and the transfer robot 4 aredisposed are partitioned by a partition wall 14 so that the cleanlinessof the area B and the area A can be separated. The partition wall 14 hasan opening for allowing semiconductor wafers to pass therethrough, and ashutter 11 is provided at the opening of the partition wall 14. Atransfer robot 20 having two hands is disposed at a position where thetransfer robot 20 can access the cleaning apparatus 5 and the threewafer supports 7, 9 and 10, and a transfer robot 21 having two hands isdisposed at a position where the transfer robot 21 can access thecleaning apparatus 6 and the three wafer supports 8, 9 and 10.

The wafer support 7 is used to transfer a semiconductor wafer betweenthe transfer robot 4 and the transfer robot 20 and has a sensor 71 fordetecting whether there is a semiconductor wafer or not. The wafersupport 8 is used to transfer a semiconductor wafer between the transferrobot 4 and the transfer robot 21 and has a sensor 72 for detectingwhether there is a semiconductor wafer or not. The wafer support 9 isused to transfer a semiconductor wafer from the transfer robot 21 to thetransfer robot 20, and has a sensor 73 for detecting whether there is asemiconductor wafer or not and rinsing nozzles 75 for supplying arinsing liquid to prevent a semiconductor wafer from drying or toconduct rinsing of a semiconductor wafer. The wafer support 10 is usedto transfer a semiconductor wafer from the transfer robot 20 to thetransfer robot 21, and has a sensor 74 for detecting whether there is asemiconductor wafer or not and rinsing nozzles 76 for supplying arinsing liquid to prevent a semiconductor wafer from drying or toconduct rinsing of a semiconductor wafer. The wafer supports 9 and 10are disposed in a common water-scatter-prevention cover which has aopening defined therein for transferring semiconductor waferstherethrough, the opening being combined with a shutter 77. The wafersupport 9 is disposed above the wafer support 10, and the wafer support9 serves to support a semiconductor wafer which has been cleaned and thewafer support 10 serves to support a semiconductor wafer to be cleaned,so that the cleaned semiconductor wafer is prevented from beingcontaminated by rinsing water which would otherwise fall thereon. Thesensors 71, 72, 73 and 74, the rinsing nozzles 75 and 76, and theshutter 77 are schematically shown in FIG. 1, and their positions andshapes are not illustrated exactly.

The transfer robot 20 and the transfer robot 21 have the respective twohands which are located in a vertically spaced relationship. Therespective upper hands of the transfer robot 20 and the transfer robot21 are used for transporting a semiconductor wafer which has beencleaned to the cleaning apparatuses or the wafer supports of the waferstation 50, and the respective lower hands of the transfer robot 20 andthe transfer robot 21 are used for transporting a semiconductor waferwhich has not cleaned or a semiconductor wafer to be polished. Since thelower hand is used to transfer a semiconductor wafer to or from areversing device, the upper hand is not contaminated by drops of arinsing water which fall from an upper wall of the reversing device.

A cleaning apparatus 22 is disposed at a position adjacent to thecleaning apparatus 5 and accessible by the hands of the transfer robot20, and another cleaning apparatus 23 is disposed at a position adjacentto the cleaning apparatus 6 and accessible by the hands of the transferrobot 21.

All the cleaning apparatuses 5, 6, 22 and 23, the wafer supports 7, 8, 9and 10 of the wafer station 50, and the transfer robots 20 and 21 areplaced in the area B. The pressure in the area B is adjusted so as to belower than the pressure in the area A. Each of the cleaning apparatuses22 and 23 is capable of cleaning both surfaces of a semiconductor wafer.

The polishing apparatus has a housing 46 for enclosing variouscomponents therein. The housing 46 constitutes an enclosing structure.The interior of the housing 46 is partitioned into a plurality ofcompartments or chambers (including the areas A and B) by partitions 14,15, 16, 24 and 47.

A polishing chamber separated from the area B by the partition wall 24is formed, and is further divided into two areas C and D by thepartition wall 47. In each of the two areas C and D, there are providedtwo turntables, and a top ring for holding a semiconductor wafer andpressing the semiconductor wafer against the turntables. That is, theturntables 34 and 36 are provided in the area C, and the turntables 35and 37 are provided in the area D. Further, the top ring 32 is providedin the area C and the top ring 33 is provided in the area D.

An abrasive liquid nozzle 40 for supplying an abrasive liquid to theturntable 34 in the area C and a dresser 38 for dressing the turntable34 are disposed in the area C. An abrasive liquid nozzle 41 forsupplying an abrasive liquid to the turntable 35 in the area D and adresser 39 for dressing the turntable 35 are disposed in the area D. Adresser 48 for dressing the turntable 36 in the area C is disposed inthe area C, and a dresser 49 for dressing the turntable 37 in the area Dis disposed in the area D. The turntables 36 and 37 may be replaced withwet-type thickness measuring devices for measuring the thickness of alayer on a semiconductor wafer. If such wet-type thickness measuringdevices are provided, then they can measure the thickness of a layer ona semiconductor wafer immediately after it is polished, and hence it ispossible to further polish the polished semiconductor wafer or control apolishing process for polishing a next semiconductor wafer based on themeasured value.

FIG. 2 shows the relationship between the top ring 32 and the turntables34 and 36. The relationship between the top ring 33 and the turntables35 and 37 is the same as that of the top ring 32 and the turntables 34and 36. As shown in FIG. 2, the top ring 32 is supported from a top ringhead 31 by a top ring drive shaft 91 which is rotatable. The top ringhead 31 is supported by a support shaft 92 which can be angularlypositioned, and the top ring 32 can access the turntables 34 and 36. Thedresser 38 is supported from a dresser head 94 by a dresser drive shaft93 which is rotatable. The dresser head 94 is supported by an angularlypositionable support shaft 95 for moving the dresser 38 between astandby position and a dressing position over the turntable 34. Thedresser 48 is similarly supported from a dresser head 97 by a dresserdrive shaft 96 which is rotatable. The dresser head 97 is supported byan angularly positionable support shaft 98 for moving the dresser 48between a standby position and a dressing position over the turntable36.

As shown in FIG. 1, in the area C separated from the area B by thepartition wall 24 and at a position that can be accessed by the hands ofthe transfer robot 20, there is provided a reversing device 28 forreversing a semiconductor wafer, and at a position that can be accessedby the hands of the transfer robot 21, there is provided a reversingdevice 28′ for reversing a semiconductor wafer. The partition wall 24between the area B and the areas C, D has two openings each for allowingsemiconductor wafers to pass therethrough, one of which is used fortransferring the semiconductor wafer to or from the reversing device 28and the other of which is used for transferring the semiconductor waferto or from the reversing device 28′. Shutters 25 and 26 are provided atthe respective openings of the partition wall 24. The reversing devices28 and 28′ have a chuck mechanism for chucking a semiconductor wafer, areversing mechanism for reversing a semiconductor wafer, and asemiconductor wafer detecting sensor for detecting whether the chuckmechanism chucks a semiconductor wafer or not, respectively. Thetransfer robot 20 transfers a semiconductor wafer to the reversingdevice 28, and the transfer robot 21 transfers a semiconductor wafer tothe reversing device 28′.

A rotary transporter 27 is disposed below the reversing devices 28 and28′ and the top rings 32 and 33, for transferring semiconductor wafersbetween the cleaning chamber (area B) and the polishing chamber (areas Cand D). The rotary transporter 27 has four stages for placing asemiconductor wafer at equal angular intervals, and can hold a pluralityof semiconductor wafers thereon at the same time. The semiconductorwafer which has been transported to the reversing device 28 or 28′ istransferred to the rotary transporter 27 by actuating a lifter 29 or 29′disposed below the rotary transporter 27 when the center of the stage ofthe rotary transporter 27 is aligned with the center of thesemiconductor wafer held by the reversing device 28 or 28′. Thesemiconductor wafer placed on the stage of the rotary transporter 27 istransported to a position below the top ring 32 or 33 by rotating therotary transporter 27 by an angle of 90°. At this time, the top ring 32or 33 is positioned above the rotary transporter 27 beforehand by aswing motion thereof. The semiconductor wafer is transferred from therotary transporter 27 to the top ring 32 or 33 by actuating a pusher 30or 30′ disposed below the rotary transporter 27 when the center of thetop ring 32 or 33 is aligned with the center of the semiconductor waferplaced on the stage of the rotary transporter 27.

The semiconductor wafer transferred to the top ring 32 or 33 is heldunder vacuum by a vacuum attraction mechanism of the top ring 32 or 33,and transported to the turntable 34 or 35. Thereafter, the semiconductorwafer is polished by a polishing surface comprising a polishing cloth ora grinding stone (or a fixed abrasive plate) attached on the turntable34 or 35. The second turntables 36 and 37 are disposed at positions thatcan be accessed by the top rings 32 and 33, respectively. With thisarrangement, a primary polishing of the semiconductor wafer can beconducted by the turntable 34 or 35, and then a secondary polishing ofthe semiconductor wafer can be conducted by the second turntable 36 or37. Alternatively, the primary polishing of the semiconductor wafer canbe conducted by the second turntable 36 or 37, and then the secondarypolishing of the semiconductor wafer can be conducted by the firstturntable 34 or 35. In this case, since the second turntable 36 or 37has a smaller-diameter polishing surface than the first turntable 34 or35, a grinding stone (or a fixed abrasive plate) which is more expensivethan a polishing cloth is attached to the second turntable 36 or 37 tothereby conduct a primary polishing of the semiconductor wafer. On theother hand, the polishing cloth having a shorter life but being cheaperthan the grinding stone (or the fixed abrasive plate) is attached to thefirst turntable 34 or 35 to thereby conduct a finish polishing of thesemiconductor wafer. This arrangement or utilization may reduce therunning cost of the polishing apparatus. If the polishing cloth isattached to the first turntable and the grinding stone (or fixedabrasive plate) is attached to the second turntable, then the turntablesystem may be provided at a lower cost. This is because the grindingstone (or the fixed abrasive plate) is more expensive than the polishingcloth, and the price of the grinding stone (or the fixed abrasive plate)is substantially proportional to the diameter of the grinding stone.Further, since the polishing cloth has a shorter life than the grindingstone (or the fixed abrasive plate), if the polishing cloth is usedunder a relatively light load such as a finish polishing, then the lifeof the polishing cloth is prolonged. Further, if the diameter of thepolishing cloth is large, the chance or frequency of the contact withthe semiconductor wafer is distributed to thus provide a longer life, alonger maintenance period, and an improved productivity of thesemiconductor devices.

After a semiconductor wafer is polished by the first turntable 34 andbefore the top ring 32 moves to the second turntable 36, a cleaningliquid is supplied from cleaning liquid nozzles 1510 disposed adjacentto the turntable 34 to the semiconductor wafer held by the top ring 32at a position where the top rind 32 is spaced from the turntable 34.Because the semiconductor wafer is rinsed before moving to the secondturntable 36, the transfer of contamination between the turntables isprevented to thus avoid cross contamination of the turntables.

Further, two-stage polishing can be performed in such a manner that apolishing cloth sold under the tradename of IC1000/SUBA400 manufacturedby Rodel Nitta corporation is used for the first polishing surface and apolishing cloth sold under the tradename of POLITEX manufactured byRodel Nitta corporation is used for the second polishing surface, andthe semiconductor wafer is first polished by the first polishingsurface, and then polished by the second polishing surface. Thistwo-stage polishing may be carried out by the use of the two large-sizedturntables even if the small-sized second turntable is not used. In theabove, although the two-stage polishing has been described as beingconducted by two different polishing cloths, it may be conducted by thesame polishing cloth or the same grinding stone. After the semiconductorwafer is polished by the first polishing surface and the secondpolishing surface, the first and second polishing surfaces are dressedby the dressers 38, 39, 48 and 49, respectively. The dressing process isa process for recovering the polishing surface of the turntable whichhas been degraded by polishing of the semiconductor wafers. This processis also called conditioning or rectification.

The semiconductor wafer which has been polished is returned to thereversing device 28 or 28′ in the reverse route to the above. Thesemiconductor wafer returned to the reversing device 28 or 28′ is rinsedby pure water or chemicals supplied from rinsing nozzles. Further, thesemiconductor wafer holding surface of the top ring 32 or 33 from whichthe semiconductor wafer has been removed is also cleaned by pure wateror chemicals supplied from cleaning nozzles, and in some cases, thesemiconductor wafer holding surface of the top ring 32 or 33 is rinsedfor preventing the semiconductor wafer holding surface from being dried.A cleaning nozzle or nozzles for cleaning the pusher are provided on thepartition wall. In order to improve yield of the semiconductor device orcleaning effect of the semiconductor wafer, the semiconductor wafer maybe rinsed by chemicals in such a state that the semiconductor wafer isheld by the top ring 32 or 33. Further, the semiconductor wafer may berinsed by chemicals in such a state that the semiconductor wafer is heldby the rotary transporter 27. Further, the lifter 29 or 29′ may becleaned by nozzles (described later).

On the right side of FIG. 2, the relationship of the rotary transporter27, the reversing device 28 or 28′, the lifter 29 or 29′, and the pusher30 or 30′ is shown. As shown in FIG. 2, the reversing units 28 and 28′are disposed above the rotary transporter 27, and the lifters 29 and 29′and the pushers 30 and 30′ are disposed below the rotary transporter 27.

Next, transport routes for transporting semiconductor wafers will bedescribed.

All software is constructed such that all units or devices are freelycombined and set in normal processing routes of the semiconductor wafersin the polishing apparatus. Examples of the processing routes are thefollowing:

1) Method (2 cassette parallel processing) in which semiconductor wafersin one wafer cassette are processed in one of the two areas C and D, andsemiconductor wafers in another wafer cassette are processed in theother of the two areas C and D;

2) Method (1 cassette parallel processing) in which semiconductor wafersin one wafer cassette are distributed into the area C and the area Darbitrarily; and

3) Method (serial processing) in which semiconductor wafers in one wafercassette are processed in one of the areas C and D, and then processedin the other of the areas C and D.

In the cleaning chamber, polished semiconductor wafers discharged fromthe polishing chambers are processed according to any one of thefollowing six processes:

A) Process in which semiconductor wafers are cleaned in two-stages bytwo arrays of cleaning apparatuses and discharged, i.e., from thecleaning apparatus 22 to the cleaning apparatus 5 and from the cleaningapparatus 23 to the cleaning apparatus 6;

B) Process in which semiconductor wafers are cleaned in three-stages byone array of cleaning apparatuses and discharged, i.e., from thecleaning apparatus 23 to the cleaning apparatus 6 and then to thecleaning apparatus 5 or in three-stages by one array of cleaningapparatuses and discharged, i.e., from the cleaning apparatus 22 to thecleaning apparatus 23 or 6 and then to the cleaning apparatus 5;

C) Process in which semiconductor wafers are cleaned in three-stages anddischarged, i.e., in one-stage by two cleaning apparatuses, i.e., eitherone of the cleaning apparatuses 22, 23 where no cleaning is beingconducted, and in two-stages by one array of cleaning apparatuses, i.e.,from the cleaning apparatus 6 to the cleaning apparatus 5;

D) Process in which semiconductor wafers are cleaned in four-stages byone array of cleaning apparatuses and discharged, i.e., from thecleaning apparatus 23 to the cleaning apparatus 6 and then to thecleaning apparatus 22 and then to the cleaning apparatus 5;

E) Process in which semiconductor wafers are cleaned in four-stages byone array of cleaning apparatuses and discharged, i.e., from thecleaning apparatus 22 to the cleaning apparatus 23 and then to thecleaning apparatus 6 and then to the cleaning apparatus 5; and

F) Process in which semiconductor wafers are cleaned in three-stages byone array of cleaning apparatuses and discharged, i.e., from thecleaning apparatus 23 to the cleaning apparatus 6 and then to thecleaning apparatus 5, after the semiconductor wafers which have beenpolished in a first stage are cleaned by the cleaning apparatus 22 andthen polished again in a second stage.

Combinations of the methods 1)-3) and the processes A)-F) provide theirrespective features as follows:

(1-A):

This combination is effective in a case where different processes arecarried out for two wafer cassettes and a case where a plurality of lotsof semiconductor wafers are discharged at a high throughput. Ifdifferent processes are carried out for the two wafer cassettes, then anapparatus configuration or arrangement provided by a combination of twodry-in and dry-out type polishing apparatuses, for example, is employed.Since this combination offers the greatest throughput, it is used toachieve a higher production capability with the same process beingcarried out on semiconductor wafers from the two wafer cassettes.

(2-A):

This combination is effective to process semiconductor wafers in onewafer cassette in a short period of time. This combination also allowssemiconductor wafers in one wafer cassette to be processed in twoarbitrary different types of processes.

(3-A):

In the case where the time required to clean a semiconductor wafer in atleast one of the two cleaning stages is longer than the time required topolish a semiconductor wafer in either one of the two polishing stages,if the two cleaning stages are carried out by one array of cleaningapparatuses, then the polishing capability is lowered because of thelong cleaning time. In this case, if the two cleaning stages are carriedout by two arrays of cleaning apparatuses, then polished semiconductorwafers can be delivered without being affected by the cleaning time.This combination is highly effective in this case.

(1-B):

This combination is used in a case where three or more types of cleaningprocess are required after the polishing process. Since the cleaningprocess is carried out by one array of cleaning apparatuses, theprocessing capability of the cleaning process according to thiscombination is reduced, and the combination is highly effective in acase where the polishing time is longer than the cleaning time.

(2-B):

This combination is used in a case where only one lot is processed, butnot a plurality of lots are processed at once as with the combination(1-B), and offers the same advantages as with the combination (1-B).

(3-B):

This combination is used in a case where three cleaning stages areneeded as with the combination (1-B).

(1-C):

This combination offers the same advantages as with the combination(1-B). If the cleaning time in the first cleaning stage is longer thanthe processing time in another wafer processing unit, then the firstcleaning stage is carried out by two cleaning apparatuses for preventingsemiconductor wafers from being jammed at the first cleaning apparatus,thereby increasing the processing capability.

(2-C):

As with the combination (1-C), this combination is used for the samereason as the combination (2-B).

(3-C):

As with the combination (1-C), this combination is used for the samereason as the combination (3-B).

(1, 2, 3-D, E):

This combination is used in a case where four cleaning stages arerequired in addition to the use of the respective polishing chambers.

(3-F):

In the two-stage polishing process, this combination is used totransport semiconductor wafers through a cleaning process before thesecond polishing stage for preventing the semiconductor wafers to whichthe abrasive liquid used in the first polishing stage is attached frombeing polished in the second polishing stage.

As described above, since the polishing apparatus according to thepresent invention has the two polishing sections having the respectiveturntables 34 and 35, one of the polishing sections can be inspected andserviced for maintenance while the polishing apparatus is in operationusing the other polishing section.

A cleaning section has the cleaning apparatuses 5, 6, 22 and 23 forcleaning semiconductor wafers. While the polishing apparatus is inoperation using at least one of the cleaning apparatuses, the othercleaning apparatuses can be inspected and serviced for maintenance.

FIGS. 3 through 22 show processes of polishing a semiconductor waferwith the polishing apparatus shown in FIG. 1. FIGS. 3 through 14 show aprocess in which a semiconductor wafer is taken out from a wafercassette CS1, polished, cleaned, and returned to the wafer cassette CS1,and a process in which a semiconductor wafer is taken out from anotherwafer cassette CS2, polished, cleaned, and returned to the wafercassette CS2. FIGS. 15 through 22 show a process in which asemiconductor wafer is taken out from the wafer cassette CS1, polished,cleaned, and returned to the wafer cassette CS1. In FIGS. 3 through 22,the wafer cassettes 1 are represented by CS1, CS2, CS3 and CS4, thetransfer robots 4, 20 and 21 are represented by RBD, RBL and RBR, andthe cleaning apparatuses 22, 23, 6 and 5 are represented by CL1, CL2,CL3 and CL4. The reversing devices 28 and 28′ are represented by TOL andTOR, the turntables 34 and 35 are represented by TTL and TTR, and thetop rings 32 and 33 are represented TRL and TRR. The wafer stages forloading in the rotary transporter 27 are represented by LR and LL, thewafer stages for unloading in the rotary transporter 27 are representedby ULR and ULL, and the wafer supports 7, 8, 9 and 10 of the waferstation 50 are represented by DSL, DSR, WS1 and WS2.

FIGS. 3 through 7 show two cassette parallel processing process in whichtwo-stage cleaning is performed.

As shown in FIGS. 3 through 7, one semiconductor wafer is processed inthe following route: the wafer cassette (CS1)→the transfer robot(RBD)→the wafer support of the wafer station (DSL)→the transfer robot(RBL)→the reversing device (TOL)→the wafer stage for loading in therotary transporter (LL)→the top ring (TRL)→the turntable (TTL)→the topring (TRL)→the wafer stage for unloading in the rotary transporter(ULL)→the reversing device (TOL)→the transfer robot (RBL)→the cleaningapparatus (CL1)→the transfer robot (RBL)→the cleaning apparatus(CL4)→the transfer robot (RBD)→the wafer cassette (CS1).

The other semiconductor wafer is processed in the following route: thewafer cassette (CS2)→the transfer robot (RBD)→the wafer support of thewafer station (DSR)→the transfer robot (RBR)→the reversing device(TOR)→the wafer stage for loading in the rotary transporter (LR)→the topring (TRR)→the turntable (TTR)→the top ring (TRR)→the wafer stage forunloading in the rotary transporter (ULR)→the reversing device (TOR)→thetransfer robot (RBR)→the cleaning apparatus (CL2)→the transfer robot(RBR)→the cleaning apparatus (CL3)→the transfer robot (RBD)→the wafercassette (CS2).

FIGS. 8 through 14 show two cassette parallel processing in whichthree-stage cleaning is performed.

As shown in FIGS. 8 through 14, one semiconductor wafer is processed inthe following route: the wafer cassette (CS1)→the transfer robot(RBD)→the wafer support of the wafer station (DSL)→the transfer robot(RBL)→the reversing device (TOL)→the wafer stage for loading in therotary transporter (LL)→the top ring (TRL)→the turntable (TTL)→the topring (TRL)→the wafer stage for unloading in the rotary transporter(ULL)→the reversing device (TOL)→the transfer robot (RBL)→the cleaningapparatus (CL1)→the transfer robot (RBL)→the wafer support of the waferstation (WS2)→the transfer robot (RBR)→the cleaning apparatus (CL3)→thetransfer robot (RBR)→the wafer support of the wafer station (WS1)→thetransfer robot (RBL)→the cleaning apparatus (CL4)→the transfer robot(RBD)→the wafer cassette (CS1).

The other semiconductor wafer is processed in the following route: thewafer cassette (CS2)→the transfer robot (RBD)→the wafer support of thewafer station (DSR)→the transfer robot (RBR)→the reversing device(TOR)→the wafer stage for loading in the rotary transporter (LR)→the topring (TRR)→the turntable (TTR)→the top ring (TRR)→the wafer stage forunloading in the rotary transporter (ULR)→the reversing device (TOR)→thetransfer robot (RBR)→the cleaning apparatus (CL2)→the transfer robot(RBR)→the cleaning apparatus (CL3)→the transfer robot (RBR)→the wafersupport of the wafer station (WS1)→the transfer robot (RBL)→the cleaningapparatus (CL4)→the transfer robot (RBD)→the wafer cassette (CS2).

FIGS. 15 through 22 show a serial processing in which three-stagecleaning is performed.

As shown in FIGS. 15 through 22, the semiconductor wafer is processed inthe following route: the wafer cassette (CS1)→the transfer robot(RBD)→the wafer support of the wafer station (DSL)→the transfer robot(RBL)→the reversing device (TOL)→the wafer stage for loading in therotary transporter (LL)→the top ring (TRL)→the turntable (TTL)→the topring (TRL)→the wafer stage for unloading in the rotary transporter(ULL)→the reversing device (TOL)→the transfer robot (RBL)→the cleaningapparatus (CL1)→the transfer robot (RBL)→the wafer support of the waferstation (WS2)→the transfer robot (RBR)→the reversing device (TOR)→thewafer stage for loading in the rotary transporter (LR)→the top ring(TRR)→the turntable (TTR)→the top ring (TRR)→the wafer stage forunloading in the rotary transporter (ULR)→the reversing device (TOR)→thetransfer robot (RBR)→the cleaning apparatus (CL2)→the transfer robot(RBR)→the cleaning apparatus (CL3)→the transfer robot (RBR)→the wafersupport of the wafer station (WS1)→the transfer robot (RBL)→the cleaningapparatus (CL4)→the transfer robot (RBD)→the wafer cassette (CS1).

In examples shown in FIGS. 3 through 22, it is described that onesemiconductor wafer is taken out from the wafer cassette (CS1), andanother semiconductor wafer is taken out from the wafer cassette (CS2).However, the wafer cassettes (CS1) and (CS2) may be used for dedicatedlysupplying the semiconductor wafers to the turntable (TTL), and the wafercassettes (CS3) and (CS4) may be used for dedicatedly supplying thesemiconductor wafers to the turntable (TTR).

Next, the components of the polishing apparatus shown in FIG. 1 will bedescribed in detail below.

Loading and Unloading Section

FIGS. 1, 23A and 23B are front and side elevational views of the loadingand unloading section.

As shown in FIGS. 1, 23A and 23B, the loading and unloading section hasfour load-unload stages 2 each for placing a wafer cassette 1 (opencassette). The load-unload stages 2 have a positioning mechanism in theform of a block configurated to match the shape of a lower portion ofthe wafer cassette 1, for holding a wafer cassette in the same positionat all times even when the wafer cassette is repeatedly placed thereon.When a wafer cassette is placed in a proper position, the presence ofthe wafer cassette is detected by a button-type sensor. A pair oftransmission type light sensors 351 are positioned above and below awafer cassette such that light between the transmission type lightsensors 351 is blocked by any wafer that projects out of position.Therefore, the transmission type light sensors 351 can detect anysemiconductor wafer that projects out of position and determine whethersemiconductor wafers are properly placed in respective slots in thewafer cassette. If any semiconductor wafer that projects out of positionis detected, then an interlocking mechanism is operated to control thetransfer robot 4 and a search mechanism 352 so as not to access theloading and unloading section.

Dummy wafer stations 353 are disposed below the respective load-unloadstages 2. Each of the dummy wafer stations 353 is capable of placing oneor more wafers thereon, and can hold a dummy wafer for use instabilizing a polishing cloth before a product wafer is processed and aQC (quality control) wafer to be delivered for confirming the status orcondition of the polishing apparatus. Each of the dummy wafer stations353 has a pair of wafer detecting sensors 354 for confirming thepresence of a semiconductor wafer therein. Each of the dummy waferstations 353 also has a sensor for detecting a semiconductor wafer thatprojects out of position, but the transmission type light sensors 351may be also used as such sensors. If no wafer cassette is placed on theload-unload stage 2, the load-unload stage 2 located above each of thedummy wafer stations 353 may be lifted, and a wafer may manually beplaced on the dummy wafer station 353. According to a standardprocedure, after a wafer cassette with wafers inserted therein is placedon any one of the load-unload stages 2, wafers are searched for, and aninstruction is sent from a control panel to indicate which wafer is tobe sent to the selected dummy wafer station. Then, the selected wafer isdelivered from the wafer cassette to the dummy wafer station by thetransfer robot 4 which can access both the wafer cassette and the dummywafer station.

A wafer search mechanism 352 is disposed below each of the load-unloadstages 2, and each of the dummy wafer stations 353, if any. The wafersearch mechanism 352 is vertically movable with a pair of wafer searchsensors 356 mounted on the tip end thereof by a driving source 355comprising a pulse motor. While the wafer search mechanism 352 is not ina wafer search operation, the wafer search mechanism 352 is kept in astandby position within the apparatus for avoiding interference withother operating members. The wafer search sensors 356 are disposed inconfronting relation to each other such that light travelingtherebetween passes horizontally through the wafer cassette as viewedfrom a side of the loading and unloading section. While the wafer searchmechanism 352 is in a wafer search operation, it moves from a positionbelow the dummy wafer station 353 to a position above a final slot inthe wafer cassette in a reciprocating manner, counts the number of timesthat the light is interrupted by a semiconductor wafer for therebycounting the number of wafers in the wafer cassette, detects thepositions of the semiconductor wafers from the pulses of the pulse motoras the driving source, and determines which slots in the wafer cassettethe semiconductor wafers are placed in. The wafer search mechanism 352also has an oblique wafer detecting function to detect an obliquelyinserted wafer when the light between the wafer search sensors 356 isinterrupted for the time corresponding to the number of pulses that isgreater than the number of pulses corresponding to the spacing betweenthe slots in the wafer cassette which has been stored in advance.

A shutter 357 that is vertically movable by an air cylinder is disposedbetween an opening in the wafer cassette and the apparatus for therebyseparating the cassette placing area and the interior of the apparatus.The shutter 357 is closed except when the transfer robot 4 transfers thesemiconductor wafers to or from the wafer cassette. A partition 358 isdisposed between the load-unload stages 2 arrayed in front of theapparatus for allowing the operator to access the processed wafercassette for replacement without touching an adjacent wafer cassettewhich is in operation.

The load-unload stages 2 have respective front sides separated from theexterior of the apparatus by a door 360. The door 360 has a lockmechanism and a sensor 361 for detecting whether the door is open orclosed. While a wafer cassette is being processed, the door 360 islocked by the lock mechanism to protect the wafer cassette and avoiddanger to the operator. When the door 360 is left open for a certainperiod of time, an alarm is issued.

There are two methods of placing a wafer cassette in the loading andunloading section.

(1) According to one method, a wafer cassette housing semiconductorwafers is placed directly on a wafer support portion. This process isemployed when a chamber of a clean room facing the loading and unloadingsection is relatively clean, i.e., has a class 100 clean roomenvironment or lower, for example.

(2) According to another method, when a chamber of a clean room facingthe loading and unloading section is relatively dirty, i.e., has a class1000 clean room environment or higher, for example, the wafer cassetteis placed in a box which is controlled in about class 100 clean roomenvironment, and delivered in the clean room and placed on the loadingand unloading section.

If the method (1) described above is employed, a filter fan unit 10000is mounted on the loading and unloading section for keeping the wafersupport portions clean at all times.

FIG. 24 shows another loading and unloading section which is operatedaccording to the method (2) described above. According to the method(2), a wafer cassette 1 is housed in a box 367 and placed on aload-unload stage 2. When the box 367 is placed on the load-unload stage2, a stage 366 attached to the load-unload stage 2 and a bottom plate363 of the box 367 are locked and fixed to each other. The bottom plate363 is attached to the box 367 so as to fully close the box 367. At thesame time that the stage 366 and the bottom plate 363 are locked to eachother, the load-unload stage 2 and the box 367 are held in intimatecontact with each other, and the box 367 and the bottom plate 363 arereleased from each other and can freely detached from each other.

The stage 366 has a lifting mechanism 362 for lifting and lowering thestage 366 and the bottom plate 363 on which the wafer cassette 1 isplaced. When it is confirmed that the stage 366 and the bottom plate 363are locked to each other, the stage 366 is lowered to introduce thewafer cassette 1 into an apparatus interior 364. If the apparatusinterior 364 is kept clean, then the wafer cassette 1 can be carriedinto the apparatus interior 364 without being exposed to an exterioratmosphere 365 which is dirtier than the apparatus interior 364. Byallowing the transfer robot 4 to move to a position adjacent to thewafer cassette 1 to receive semiconductor wafers in the wafer cassette 1located below the load-unload stage 2, the semiconductor wafer can befed into the polishing apparatus.

Cleaning Apparatus

Of the cleaning apparatuses mounted in the polishing apparatus, thecleaning apparatuses 22 and 23 have a roll-shaped sponge rotatable aboutits own axis and pressed against a semiconductor wafer to clean thereverse side of the semiconductor wafer. For cleaning the face side(polished surface) of the semiconductor wafer, the cleaning apparatuses22 and 23 may have a roll type cleaning mechanism for rotating andpressing a roll-shaped sponge against the semiconductor wafer, or apencil type cleaning mechanism for rotating and pressing a hemisphericalsponge against the semiconductor wafer. Either one of the two types canbe selected. Further, a megasonic type cleaning mechanism for cleaningthe semiconductor wafer with a cleaning liquid to which ultrasonicvibration is applied may be added. The cleaning apparatuses 22 and 23serve mainly to remove particles from the semiconductor wafers.Regardless of the type of the cleaning apparatus, each of the cleaningapparatuses can supply three or more kinds of cleaning liquid to theface (polished surface) and reverse sides of the semiconductor wafer.The cleaning liquid may comprise pure water.

Each of the cleaning apparatuses 5 and 6 is capable of rinsing thereverse side of a semiconductor wafer. For cleaning the face side of thesemiconductor wafer, the cleaning apparatuses 5 and 6 may conductcleaning by the pencil type cleaning mechanism for rotating and pressinga hemispherical sponge against the semiconductor wafer and cleaning bythe megasonic type cleaning mechanism for cleaning the semiconductorwafer with a cleaning liquid to which ultrasonic vibration is applied.Each of the cleaning apparatuses 5 and 6 can supply three or more kindsof cleaning liquid to the face (polished surface) and reverse sides ofthe semiconductor wafer. The cleaning liquid may comprise pure water. Astage for chucking a semiconductor wafer may be rotated at a high speed,and has a function for drying a cleaned wafer.

Instead of the megasonic type cleaning mechanism, each of the cleaningapparatuses may have cavitation jet type cleaning mechanism utilizing acavitation effect in which a cavitation is applied to a cleaning liquidbecause it is as effective as the megasonic type.

As shown in FIG. 1, the cleaning apparatuses 5, 6, 22 and 23 haverespective openings associated with respective shutters 5 a, 5 b, 6 a, 6b, 22 a and 23 a which can be opened only when the semiconductor wafersare to be introduced therein or removed therefrom. The openings with theshutters 5 b, 6 b serve to allow the cleaned and dried semiconductorwafer to pass therethrough. That is, the polished, cleaned and driedsemiconductor wafer may be transferred from the cleaning apparatuses 5,6 through the openings with the shutters 5 b, 6 b to the wafer cassette1 by the transfer robot 4. Further, the polished, cleaned and driedsemiconductor wafer may be transferred from the cleaning apparatuses 5,6 through the openings with the shutters 5 a, 6 a and the wafer station50 to the wafer cassette 1 by the transfer robot 4.

Each of the cleaning apparatuses 5, 6, 22 and 23 has a plurality ofcleaning liquid supply lines associated with constant-rate flow valvesthat can be controlled by an air pressure. With the constant-rate flowvalves combined with electropneumatic regulators for controlling the airpressure, the flow rate in the cleaning liquid supply lines can freelybe established from a control panel. Cleaning liquids supplied to thecleaning apparatuses, and cleaning processes and cleaning time thereforcan be set from the control panel.

Guides are mounted on a base of the cleaning chamber (area B), and thecleaning apparatuses are mounted in the guides, so that the cleaningapparatuses can easily be replaced with different type cleaningapparatuses. There are provided positioning mechanisms for placingreplaced cleaning apparatuses in the same position.

Air Flow

The polishing apparatus is divided into four areas including the loadingand unloading section (area A), the cleaning chamber (area B), thepolishing chambers (areas C and D).

Air flows in the polishing chambers (areas C and D) are classified intofour air flows. The first air flow occurs around the turntables for thepurpose of preventing dust such as slurry from being scattered. Thesecond air flow takes place around the pusher for the purpose ofpreventing mist of cleaning liquid produced when the semiconductorwafers, the pusher and the top rings are cleaned in the pusher regionfrom being scattered. The third air flow is caused in the entire wetregion in the polishing chambers by opening doors leading to the wetatmosphere in the polishing chambers and simultaneously discharging airfrom the entire wet region for preventing the wet atmosphere from goingout of the polishing chambers when expendables such as polishing clothsare replaced. The fourth air flow is developed to draw heat dischargedfrom motors and other control units. Since all the air flows are createdby exhausting air in the polishing chambers to the exterior thereof, theoverall polishing chambers develop a negative pressure therein ascompared with the pressure developed outside the polishing chambers. Forproducing the third air flow, in order to discharge air at the same timethat the doors are opened, it is necessary to automatically open dampersin response to signals from door sensors. To meet such a requirement,actuators are attached to the dampers for opening and closing thedampers.

Other exhaust air passages have dampers for regulating the respectiveamounts of exhaust air. The amounts of exhaust air in the respectiveexhaust passages are regulated by the dampers to achieve an overalldischarged air balance. A pressure switch is disposed in an airdischarge port of the polishing apparatus for enabling the polishingapparatus to issue an alarm or shutting off the polishing apparatus ifno air is discharged, so that the polishing apparatus can be operatedsafely.

FIG. 25 shows air flows in the cleaning chamber (area B). As shown inFIG. 25, a structure for producing air flows in the cleaning chamber(area B) includes a filter fan unit 194 comprising a filter 190 (e.g.,an ULPA filter or a HEPA filter) and fans 191 which are mounted on theceiling of the cleaning chamber (area B), a duct 193 for returning airin the cleaning chamber (area B) to the filter fan unit 194 to circulateair, individual air discharge passages 197 for discharging air from thefour cleaning apparatuses, and an air inlet port 195 combined with thefilter fan unit 194. A chemical filter may be added for removing ions(e.g., NH₄ ⁻, K⁺, etc.) contained in the air.

Air is supplied into the cleaning chamber (area B) through the filter190 by the fans 191 of the filter fan unit 194, and introduced as adownflow adjusted by a mechanism 198 for regulating the air flow rate ofthe fans 191. The mechanism 198 comprises an inverter and athyristor-controlled AC power regulator. Air E discharged from thecleaning apparatuses is introduced from the air inlet port 195 combinedwith the filter fan unit 194 into the cleaning chamber (area B). Air Fother than the air discharged from the cleaning apparatuses is deliveredvia the duct 193 to the filter fan unit 194, and passes through thefilter 190 as clean air that is returned to the cleaning chamber (areaB) for air circulation. The air pressure in the cleaning chamber (areaB) is adjusted by the opening degree of a damper 192 which is disposedin the duct 193.

The air from the cleaning apparatuses is discharged via the individualair discharge passages. These individual air discharge passages may becombined together for discharging the air from the cleaning apparatusesif cleaning chemicals used in the cleaning apparatuses do not produce anadverse effect due to a chemical reaction therebetween. Dampers aredisposed in the respective air discharge passages to produce balancedamounts of discharged air.

A structure for producing air flows in the loading and unloading section(area A) is the same as the structure for producing air flows in thecleaning chamber (area B) except that the individual air dischargepassages from the cleaning apparatuses are dispensed with. The processof regulating the air flows in the loading and unloading section (areaA) is also the same as the process of regulating the air flows in thecleaning chamber (area B) except that the air pressure in the loadingand unloading section (area A) is regulated so as to be higher than theair pressure in the cleaning chamber (area B).

The air in the polishing apparatus is circulated by the return duct 193and reused via the filter 190. Therefore, the amount of clean airintroduced from the clean room into the polishing apparatus is reducedfor saving energy.

Air flows in the entire polishing apparatus are regulated such that theair pressure in the loading and unloading section (area A) where ahighest level of cleanliness is required is highest, and progressivelylower in the order of the cleaning chamber (area B) and the polishingchambers (areas C and D). If the level of cleanliness in the clean roomis lower than the level of cleanliness required for the semiconductorwafers, then the air pressures in the entire polishing apparatus can beregulated to make the air pressures in the polishing apparatus higherthan the air pressure in the clean room. If the level of cleanliness inthe clean room is equal to or higher than the level of cleanlinessrequired for the semiconductor wafers, then the air pressures in theentire polishing apparatus can be regulated to make the air pressures inthe polishing apparatus lower than the air pressure in the clean room.

Transfer Robot

FIG. 26 is a side elevational view of the transfer robot 4. As shown inFIG. 26, the transfer robot 4 has a θ-axis 120 for rotating a robotbody, an R1 (upper hand) and R2 (lower hand)-axis 121-1, 121-2 (i.e.X-axis, Y-axis) for extending or contracting the hand, a Z-axis 122 in avertical direction, and an X-axis 123 in a direction in which the wafercassettes are arrayed. The Z-axis of the robot may be incorporated in arobot body 124. The upper and lower hands may have respective vacuumlines therein, and may be used as a vacuum attraction-type hand.Further, in order to prevent the reverse side of the semiconductor wafer101 from being contaminated, the upper hand may comprise a thin recesssupport-type hand 125 made of ceramics for supporting the peripheraledge of the semiconductor wafer. The thin recess support-type hand 125is effective if used in a transfer process for removing wafers from thecleaning apparatuses 5 and 6 and returning the wafers in the wafercassette 1. That is, the thin recess support-type hand 125 is preferablefor transferring the semiconductor wafers which have been cleaned. Ifthere is provided a thickness measuring unit for measuring the thicknessof a layer on the semiconductor wafer, then the thin recess support-typehand 125 is used to transfer wafers to and from the thickness measuringunit. The lower hand comprises a vacuum attraction-type hand 126 made ofceramics and having two support portions branched from a hand body. Thevacuum attraction-type hand 126 has a vacuum line therein. The hand 126serves to take out a semiconductor wafer from the wafer cassette 1 andto transfer the semiconductor wafer to the wafer station 50.

FIG. 27 is a perspective view of the transfer robot 20 or 21. As shownin FIG. 27, the transfer robot 20 or 21 has a θ-axis 120 for rotating arobot body, an R1 (upper hand) and R2 (lower hand)-axis 121-1, 121-2(including X-axis, Y-axis) for extending or contracting the hand, and aZ-axis 122 in a vertical direction. Further, the upper hand 125 and thelower hand 126 are the recess support-type hand. The upper hand 125 ofthe transfer robot 20 can access the cleaning apparatus 22, the cleaningapparatus 5, and the wafer support 9 and 10 of the wafer station 50. Thelower hand 126 of the transfer robot 20 can access the wafer support 7of the wafer station 50, the cleaning apparatus 22, and the reversingdevice 28. Further, the upper hand 125 of the transfer robot 21 canaccess the cleaning apparatus 23, the cleaning apparatus 6, and thewafer supports 9 and 10 of the wafer station 50. The lower hand 126 ofthe transfer robot 21 can access the wafer support 8 of the waferstation 50, the cleaning apparatus 23, and the reversing device 28′. InFIG. 27, the upper hand 125 and the lower hand 126 are shown as holdingthe semiconductor wafer 101, respectively.

Wafer Station

FIGS. 28A through 28E show the wafer station. FIG. 28A is a frontelevational view of the wafer station, FIG. 28B is a side elevationalview of the wafer station, FIG. 28C is a view of the wafer station asviewed in the direction indicated by the arrow I, FIG. 28D is a view ofthe wafer station as viewed in the direction indicated by the arrow II,and FIG. 28E is a view of the wafer station as viewed in the directionindicated by the arrow III.

As shown in FIGS. 28A through 28E, the wafer station 50 comprises thewafer supports 7, 8, 9 and 10 capable of simultaneously holding fourwafers. The wafer station 50 is roughly divided into dry stationscomposed of the wafer supports 7 and 8 which are horizontally spacedfrom each other, and wet stations composed of the wafer supports 9 and10 which are vertically spaced from each other.

The dry stations 7 and 8 serve as a wafer support for temporarilysupporting a semiconductor wafer before it is polished. The dry station8 can be accessed by the transfer robot 4 and the transfer robot 21, andallows a semiconductor wafer transferred from the transfer robot 4 tothe transfer, robot 21 therethrough which transfers the semiconductorwafer to the right-hand polishing section. Similarly, the dry station 7allows a semiconductor wafer transferred from the transfer robot 4 tothe transfer robot 20 therethrough which transfers the semiconductorwafer to the left-hand polishing section. Since the wafer supports areprovided respectively for the transfer robots 20 and 21; dedicatedroutes to the respective polishing chambers are available to supply thesemiconductor wafers to be processed to the polishing chambers at alltimes without being blocked by a longer polishing time on one of theturntables than on the other turntable when the polishing times in therespective polishing processes on the turntables differ from each other.

The semiconductor wafers taken out from the wafer cassette under vacuumattraction by the transfer robot 4 are transferred to the dry stations 7and 8. Since the positional accuracy of semiconductor wafers in thewafer cassette is not so high, the positional accuracy of asemiconductor wafer held by the vacuum attraction hand of the robot isnot so high. In order to absorb such positional accuracy errors andallows semiconductor wafers to be transferred to and from subsequentrobot hands, guide blocks 78 and 79 for placing semiconductor wafersthereon have positioning tapers 180 for centering of the semiconductorwafers. Since wafer deviations in the wafer cassette are larger than inother mechanisms, the vertical length of the tapers of the guide blocksneed to be large. The transfer robot 4 positions its lower hand withinthe guide blocks of the dry stations 7 and 8, and performs the vacuumbreak of the hand to drop the semiconductor wafers therefrom, and totransfer the semiconductor wafers to the guide blocks by which thesemiconductor wafers are centered. The dry stations 7 and 8 havetransmission type light sensors 71 and 72, respectively, for detectingwhether there is a semiconductor wafer or not in the dry stations 7 and8.

Because the dry stations 7 and 8 are positioned intermediate between thecleaning area and the dry area, the shutter 11 is provided to separatethose areas from each other in order to prevent the atmospheres in theareas having different levels of cleanliness from being mixed with eachother. The shutter 11 is normally closed, but is opened only when thetransfer robot 4 gains access to the dry stations 7 and 8.

The wet stations 9 and 10 serve as wafer supports for supporting thesemiconductor wafers which have been polished. The wet stations 9 and 10can be accessed by the transfer robots 20 and 21, respectively, andallow the semiconductor wafers to be transferred between the transferrobots 20 and 21. The wet station 9 serves as a wafer support forplacing a semiconductor wafer which has been cleaned at least once, andthe wet station 10 serves as a wafer support for placing a semiconductorwafer which is subjected to a cleaning process whose number of cleaningstages is smaller than that of the semiconductor wafer placed on the wetstation 9. Inasmuch as the wet stations 9 and 10 are used separatelydepending on the level of cleanliness, it is possible to preventcontamination from being diffused via the stations.

Each of the wet stations 9 and 10 has a wafer guide comprising pins, andis compatible with both a semiconductor wafer having an orientation flatand a semiconductor wafer having a notch. Since the wet stations 9 and10 are of a structure having pins for point-to-point contact with thesemiconductor wafers, they are effective to prevent contamination frombeing diffused via the stations. The wet stations 9 and 10 havetransmission type light sensors 73 and 74, respectively, for detectingwhether there is a semiconductor wafer or not in the wet stations 9 and10.

The wet stations have respective nozzles 75 and 76 for preventingsemiconductor wafers from being dried and cleaning the semiconductorwafers by supplying a cleaning liquid to both upper and lower surfacesof the semiconductor wafers. A local air discharge line is provided forpreventing mist of the cleaning liquid from being scattered around fromthe interior of the wafer station 50. The cleaning liquid may be any ofvarious liquids including pure water, ion water or the like depending onthe type of layer (film) to be cleaned.

In order to make the wet stations water-tight, the wet stations have theshutter 77 disposed at the opening for the transfer robots 20 and 21 totransfer the semiconductor wafers therethrough, the shutter 77 beingvertically movable by an air cylinder 81. The shutter 77 is normallyclosed, and is opened only when the transfer robots 20 and 21 access thestations.

Reversing Device

FIGS. 29A and 29B show the reversing device. FIG. 29A is a plan view ofa reversing device, and FIG. 29B is a side elevational view, partly incross section, of the reversing device. Since the reversing devices 28and 28′ are of an identical structure, only the reversing device 28 willbe described below. As shown in FIGS. 29A and 29B, the reversing device28 has a pair of arcuate arms 230 supporting a plurality of (e.g., six)pins 231 fixed thereto which have grooves for clamping a semiconductorwafer therein. The arms 230 can be opened and closed in response tomovement of a shaft 234 that can be pushed and pulled by an air cylinder232 and a compression spring 233. When the air cylinder 232 is extended,the arms 230 are opened thereby. When the air cylinder 232 iscontracted, the arms 230 are closed under the force of the compressionspring 233. The shaft 234 and a tip end of the air cylinder 232 arespaced from each other by a distance, and the shaft 234 is pulled backuntil a stopper 235 contacts an end block 236 under the bias of thecompression spring 233.

The end block 236 is adjusted such that when a semiconductor wafer 101is chucked, a clearance of 1 mm is created between the stopper 235 andthe end block 236. The stopper 235 has a slit defined therein, and atransmission type light sensor 237 is positioned to detect light thathas passed through the slit when the semiconductor wafer 101 is clampedby the arms 230. Therefore, when the semiconductor wafer 101 is notclamped or cannot be clamped properly, the transmission type lightsensor 237 does not detect light. Therefore, the transmission type lightsensor 237 is capable of recognizing whether the semiconductor wafer 101is present or not in the reversing device 28.

A slide mechanism for the shaft 234 and a pulley 238 are connected toeach other, and the pulley 238 is coupled to a pulley 240 fixed to ashaft end of a stepping motor 239 through a belt 241. When the steppingmotor 239 is energized, the arms 230 are rotated about a horizontalaxis.

As shown in FIG. 1, the shutters 25 and 26 are disposed between thereversing devices 28 and 28′ and the transfer robots 20 and 21 forseparating the polishing chambers with the reversing devices disposedtherein from the cleaning chamber with the transfer robots disposedtherein. For transferring the semiconductor wafers, the shutters 25 and26 are opened, and the hands of the transfer robots 20 and 21 move inand out of the openings. When the hands of the transfer robots 20 and 21do not move in and out of the openings, the shutters 25 and 26 areclosed, providing a water-proof mechanism for allowing the semiconductorwafers and the chuck fingers fixed to the arms to be cleaned.

Next, the operation of the reversing device will be described withreference to FIGS. 29A and 29B.

The transfer robot 20 and the lifter 29 can access the reversing device28 and transfer the semiconductor wafer to the reversing device 28. Thetransfer robot 21 and the lifter 29′ can access the reversing device 28′and transfer the semiconductor wafer to the reversing device 28′.

The reversing device 28 waits for the semiconductor wafer which isconveyed by the transfer robot 20 or the lifter 29 in such a state thatthe arms 230 are opened. The arms 230 are closed when the semiconductorwafer conveyed by the lower hand of the transfer robot 20 or the lifter29 is positioned in the same vertical height as wafer holding grooves ofpins 231 fixed to the arms 230 and the center of the semiconductor waferis substantially positioned at the center of the pin arrangement on thearms 230 and after a signal indicative of completion of movement fromthe transfer robot 20 or the lifter 29 is generated. After the presenceof the semiconductor wafer 101 is confirmed by a sensor 237, the hand ofthe transfer robot 20 is lowered to a certain height and is thenretracted. Alternatively, after the presence of the semiconductor wafer101 is confirmed by the sensor 237, the lifter 29 is lowered. In thismanner, the semiconductor wafer 101 is transferred from the transferrobot 20 or the lifter 29 to the reversing device 28. The semiconductorwafer 101 transferred to the reversing device 28 is reversed byactuating the arms 230 with the stepping motor 239. The reversedsemiconductor wafer 101 is kept in the same condition until the transferrobot 20 or the lifter 29 accesses the reversing device 28 to receivethe semiconductor wafer therefrom.

The reversing operation of the semiconductor wafer is carried out beforeand after polishing of the semiconductor wafer. In case of reversing thesemiconductor wafer 101 which has been polished, in order to preventabrasive liquid or ground-off particles attached to the semiconductorwafer 101 during polishing from being dried on the semiconductor wafer101, the semiconductor wafer 101 is rinsed by a cleaning liquid duringor after reversing of the semiconductor wafer. The cleaning liquid usedto rinse the semiconductor wafer 101 comprises pure water or a chemicalliquid, and is applied from spray nozzles at a required rate under arequired pressure at an optimum angle for a desired period of time. Therinsing process enables a subsequent cleaning process to be conducted ina sufficient cleaning performance. While the semiconductor wafer 101 iswaiting on the reversing device 28, the cleaning liquid continues to besupplied to the semiconductor wafer 101. However, in view of the runningcost, the cleaning liquid may be supplied intermittently to reduce itsamount in use.

While the reversing device 28 is not clamping the semiconductor wafer101, the grooves for clamping the semiconductor wafer 101 andsurrounding areas thereof may be cleaned by the cleaning liquid toprevent the semiconductor wafer 101 from being contaminated by membersthat will contact the semiconductor wafer 101.

Lifter

FIG. 30 is a vertical cross-sectional view of the lifter. The lifter 29and 29′ have the same structure, and hence only the lifter 29 will bedescribed. The lifter 29 comprises a stage 260 for placing asemiconductor wafer thereon and an air cylinder 261 for lifting andlowering the stage 260. The air cylinder 261 and the stage 260 arecoupled by a shaft 262 which is vertically movable. The stage 260 hasthree support portions 263 disposed at angularly equal intervals in acircumferential direction and extending radially outwardly. The threesupport portions 263 are arranged in the angularly equal intervals sothat the semiconductor wafer having an orientation flat can be held andare reliably transported. The three support portions 263 are disposed atpositions where they are not aligned with the pins 231 for chucking thesemiconductor wafer in the reversing device 28. That is, the firstperipheral edge of the semiconductor wafer held by the pins 231 does notcorrespond to the second peripheral edge of the semiconductor wafer heldby the support portions 263 of the lifter 29. The wafer support portions263 of the lifter 29 which performs the transfer of the semiconductorwafer to the reversing device 28 or the rotary transporter 27 haverespective support surfaces for supporting the semiconductor waferthereon, and respective taper surfaces extending radially outwardly andupwardly from the support surfaces for centering the semiconductor waferwhen the semiconductor wafer is placed on the support surfaces.

The wafer support surfaces of the stage 260 is raised by actuation ofthe air cylinder 261 to a position where the semiconductor wafer is heldby the reversing device 28. A stopper 264 having a shock absorbingfunction is provided to stop raising of the stage 260. When a stopperbase 265 fixed to the shaft 262 contacts the stopper 264, furtheractuation of the air cylinder 261 is stopped, and the lifting of thestage 260 fixed to the shaft 262 is simultaneously stopped. By adjustingthe location of the stopper 264, the lifting height of the stage 260 canbe adjusted to a transfer position of the semiconductor wafer betweenthe lifter 29 and the reversing device 28. Sensors 266 and 267 areprovided on the air cylinder 261 to detect completion of lifting andlowering of the air cylinder 261, respectively.

Next, the operation of the lifter having the above structure will bedescribed. The lifter 29 constitutes a wafer transfer mechanism fortransferring the semiconductor wafer between the reversing device 28 andthe rotary transporter 27. The semiconductor wafer to be polished istransferred from the transfer robot 20 to the reversing device 28.Thereafter, the semiconductor wafer is reversed by the reversing device28 to cause a pattern surface (the surface on which semiconductor deviceis formed) of the semiconductor wafer to face downward. The stage 260 ofthe lifter 29 is raised toward the semiconductor wafer held by thereversing device 28 and is stopped immediately below the semiconductorwafer. When the sensor 266 provided on the air cylinder 261 detects thestop of the lifter 29 at a position where the stage 260 is locatedimmediately below the semiconductor wafer, the reversing device 28releases the semiconductor wafer by opening the arms 230 and thesemiconductor wafer is placed on the stage 260 of the lifter 29.Thereafter, the lifter 29 is lowered while holding the semiconductorwafer thereon. While the semiconductor wafer is lowered by the lifter29, the semiconductor wafer is transferred to the rotary transporter 27.At this time, the semiconductor wafer is placed on the pins of therotary transporter 27. After the semiconductor wafer is transferred tothe rotary transporter 27, the lifter 29 continues to be operated tolower the stage 260, and then is stopped when the stage 260 is loweredby the stroke of the air cylinder 261.

The semiconductor wafer which has been polished is transferred from therotary transporter 27 to the reversing device 28 by the lifter 29. Thatis, the semiconductor wafer which has been polished is transported bythe rotary transporter 27 to the position above the lifter 29. At thistime, the stage 260 of the lifter 29 is located immediately below therotary transporter 27. After it is confirmed that the semiconductorwafer placed on the rotary transporter 27 is located at the positionimmediately above the stage 260 of the lifter 29 and the movement of thesemiconductor wafer is stopped, the stage 260 of the lifter 29 starts tobe raised. The stage 260 of the lifter 29 receives the semiconductorwafer from the rotary transporter 27 while the stage 260 is lifted.Thereafter, the stage 260 of the lifter 29 continues to be lifted. Atthis time, the reversing device 28 waits for the semiconductor wafer insuch a state that the arms 230 are opened to be ready for cramping thesemiconductor wafer. The lifting of the semiconductor wafer is stoppedat the position where the semiconductor wafer is horizontally alignedwith the wafer holding grooves of the pins 231 on the arms 230. Thecompletion of lifting of the stage 260 in the lifter 29 is detected bythe sensor 266 provided on the air cylinder 261, and the detectingsignal by the sensor 266 is sent to a controller of the polishingapparatus to allow the controller to recognize the completion of liftingof the stage 260. When the controller of the polishing apparatusreceives the detecting signal, the reversing device 28 is operated toclose the arms 230. By this operation, the semiconductor wafer is heldby the reversing device 28. After it is confirmed that the semiconductorwafer is held by the reversing device 28, the stage 260 of the lifter 29is lowered.

Rotary Transporter

FIGS. 31 and 32 show the rotary transporter, and FIG. 31 is a plan viewof the rotary transporter and FIG. 32 is a vertical cross-sectional viewof the rotary transporter. As shown in FIGS. 31 and 32, the rotarytransporter 27 for transporting the semiconductor wafer 101 has fourwafer support stages at angularly equal intervals of 90°, and each ofthe four wafer support stages has six pins 201 standing on the stage forsupporting the semiconductor wafer at six points. The semiconductorwafer can be supported by at least three pins, but in this embodiment,the six pins 201 are provided for supporting both of the semiconductorwafer having an orientation flat and the semiconductor wafer having anotch. A taper surface 202 having a taper angle of 15° to 25° from theperpendicular is formed at the forward end portion of the pin 201 toallow the semiconductor wafer to be centered when the semiconductorwafer is transferred.

The wafer detecting sensors 500 are provided at positions spaced fromthe rotary transporter 27. The sensor 500 is a photosensor comprising alight emitting element 500 a and a light receiving element 500 b, and isnot moved with the stages of the rotary transporter 27. The conditionsof the semiconductor wafers which are placed on the stages aredetermined in the respective stages of the rotary transporter 27. To bemore specific, the rotary transporter 27 comprises two load stages (theright and left sides) for placing the semiconductor wafer to be polishedand two unload stages (the right and left sides) for placing thesemiconductor wafer which has been polished. The conditions of thesemiconductor wafers placed on the respective stages are always fixed,and the rotary transporter 27 has a stage 210 for placing thesemiconductor wafer to be polished on the turntable 34, a stage 211 forplacing the semiconductor wafer which has been polished on the turntable34, a stage 212 for placing a semiconductor wafer to be polished on theturntable 35, and a stage 213 for placing the semiconductor wafer whichhas been polished on the turntable 35.

Rinsing nozzles 1501, 1502, 1503 and 1504 for supplying a cleaningliquid to the semiconductor wafer are provided above or below the rotarytransporter 27 and in the positions spaced from the rotary transporter27. The rinsing nozzles 1501 to 1504 are stationary and are not rotatedwith the stages. Pure water or ionic water is mainly used as a cleaningliquid. A separator 204 is provided on the rotary transporter 27 so asto separate the wafer support stages 210 to 213 from one another forpreventing the slurry or the cleaning liquid used for cleaning thesemiconductor wafer or the top ring from being scattered around. Therotary transporter 27 is coupled to a servomotor 205, and thesemiconductor wafers on the rotary transporter 27 are transported bydriving the servomotor 205. A home position sensor 206 is provided onthe lower portion of the rotary transporter 27, and positioning of thewafer transfer position is controlled by the home position sensor 206and the servomotor 205. The transfer positions which can be positionedare three positions at angular intervals of 90° with respect to the homeposition as a center.

Next, the operation of the rotary transporter 27 having the abovestructure will be described. FIG. 31 shows the home position of therotary transporter 27. The rotary transporter 27 is rotatedcounterclockwise by an angle of 90°, and the stage 210 is located abovethe lifter 29.

The semiconductor wafer 101 to be transferred to the top ring 32 istransferred to the reversing device 28 by the transfer robot 20. Thesemiconductor wafer 101 is held by the reversing device 28, and then isreversed, i.e. turned upside down. The reversed semiconductor wafer 101is received by the lifter 29, and then lowered. While the semiconductorwafer 101 is lowered by the lifter 29, the semiconductor wafer 101 iscentered by the taper surfaces 202 of the pins 201 on the wafer supportstage 210, and placed on the shoulder of the pins 201. After thesemiconductor wafer 101 is placed on the pins 201, the lifter 29continues to be operated to cause the stage 260 to be lowered until thestage 260 does not interfere with the rotary transporter 27 even whenthe rotary transporter 27 is rotated. Thereafter, the rotary transporter27 is rotated clockwise by an angle of 90°, and the semiconductor wafer101 on the rotary transporter 27 is positioned above the pusher 30.After positioning of the rotary transporter 27 is completed, the pusher30 is operated, and the semiconductor wafer 100 is transferred to thetop ring 32 located above the rotary transporter 27.

The semiconductor wafer 101 polished by the top ring 32 is moved towardthe wafer support stage 211 of the rotary transporter 27 located belowthe top ring 32 by the pusher 30. The semiconductor wafer 101transferred from the top ring 32 to the pusher 30 is centered by thetaper surfaces 202 of the pins 201 on the wafer support stage 211, andthen placed on the shoulders of the pins 201. After the semiconductorwafer 101 is placed on the wafer support stage 211, the pusher 30continues to be operated so that the pusher 30 does not interfere withthe rotary transporter 27. Thereafter, the rotary transporter 27 isrotated counterclockwise by an angle of 90°, and the semiconductor wafer101 on the stage 211 is positioned above the lifter 29. Afterpositioning of the rotary transporter 27 is completed, the stage 260 ofthe lifter 29 is raised, and the semiconductor wafer 101 is received bythe stage 260 from the wafer support stage 211 and transported to thereversing device 28.

Pusher

FIG. 33, and FIGS. 34A through 34E show a pusher, and FIG. 33 is avertical cross-sectional view of the pusher and FIGS. 34A through 34Eare views for explaining operation of the pusher. The pusher 30 and 30′have the same structure, and hence only the pusher 30 will be described.

As shown in FIG. 33, a guide stage 141 for holding the top ring isprovided above a hollow shaft 140, and a spline shaft 142 is provided inthe hollow shaft 140. A push stage 143 is provided above the splineshaft 142. An air cylinder 145 is coupled to the spline shaft 142through a flexible joint 144. Two air cylinders are disposed verticallyin series. The lower air cylinder 146 serves to lift and lower the guidestage 141 and the push stage 143, and lifts and lowers the hollow shaft140 together with the air cylinder 145. The air cylinder 145 serves tolift and lower the push stage 143.

A linear way 149 movable in directions of an X-axis and a Y-axis isprovided to allow the top ring guide 148 to have an alignment mechanism.The guide stage 141 is fixed to the linear way 149, and the linear way149 is fixed to the hollow shaft 140. The hollow shaft 140 is held by abearing case 151 through a slide bush 150. The stroke of the aircylinder 146 is transmitted to the hollow shaft 140 through acompression spring 152.

The push stage 143 is located above the guide stage 141, and a push rod160 extending downwardly from the center of the push stage 143 passesthrough a slide bush 147 located at the center of the guide stage 141 toallow the push rod 160 to be centered. The push rod 160 contacts theupper end of the spline shaft 142. The push stage 143 is verticallymoved by the air cylinder 145 through the spline shaft 142, so that thesemiconductor wafer 101 is loaded on the top ring 32. Compressionsprings 159 are provided at the peripheral portion of the push stage143.

Three top ring guides 148 are provided at the outer circumferentialportion of the guide stage 141. Each of the top ring guides 148 has atwo-step structure, the upper step 200 serves as a contact portion withthe lower surface of the guide ring 301 of the top ring 32 or 33, andthe lower step 201 serves as a support portion for supporting thesemiconductor wafer 101. A taper surface 208 having an angle of 25° to35° from the perpendicular is formed at the upper step 200 for guidingthe guide ring 301 toward the upper step 200, and a tapered surface 207having an angle of 10° to 20° from the perpendicular is formed at thelower step 201 for guiding the semiconductor wafer 101 toward the lowerstep 201. When the semiconductor wafer 101 is unloaded from the top ring32, the top ring guides 148 receive the peripheral edge of thesemiconductor wafer.

A guide sleeve 153 is fixed to the guide stage 141 to prevent water fromentering the central part of the guide stage 141 and to guide the guidestage 141 so that the guide stage 141 is returned to its originalposition. A center sleeve 154 located inside of the guide sleeve 153 isfixed to the bearing case 151 for centering the guide stage 141. Thepusher is fixed to a motor housing 104 in the polishing section throughthe bearing case 151.

A V-ring 155 is used to prevent water from entering between the pushstage 143 and the guide stage 141, and has a lip held in contact withthe guide stage 141 to prevent water from passing therethrough. When theguide stage 141 is elevated, the volume of a portion G increases, thuslowering the pressure to thereby draw water. In order to prevent waterfrom being drawn, the V-ring 155 has a hole 202 defined in an inner sidethereof to prevent the pressure from being lowered.

A shock absorber 156 is provided for positioning of the top ring guides148 in a vertical direction and for shock-absorbing when the top ringguides 148 contact the top ring 32. In each of the air cylinders 145 and146, upper and lower limit sensors are provided for detecting theposition of the pusher in a vertical direction. That is, sensors 203 and204 are provided on the air cylinder 145, and sensors 205 and 206 areprovided on the air cylinder 146. A cleaning nozzle or nozzles forcleaning the pusher are provided to prevent the slurry attached to thepusher from contaminating the semiconductor wafer. A sensor forconfirming the presence or absence of the semiconductor wafer on thepusher may be provided. The control of the air cylinders 145 and 146 areperformed by double solenoid valves, respectively. The pushers 30 and30′ are dedicatedly provided for the top rings 32 and 33, respectively.

Next, the operation of the pusher having the above structure will bedescribed below.

-   1) Loading a semiconductor wafer

As shown in FIG. 34A, the semiconductor wafer 101 is transported to aposition above the pusher 30 by the rotary transporter 27. When the topring 32 is located in a loading position above the pusher 30 and doesnot hold the semiconductor wafer, as shown in FIG. 34B, the push stage143 is raised by the air cylinder 145. When the completion of raising ofthe push stage 143 is detected by the sensor 203, as shown in FIG. 34C,the guide stage 141 and the components associated with the guide stage141 are raised by the air cylinder 146. While the guide stage 141 israised, the guide stage 141 passes through the wafer holding position ofthe rotary transporter 27. At this time, the semiconductor wafer 101 iscentered by the taper surfaces 207 of the top ring guides 148, and thepattern surface except peripheral portion of the semiconductor wafer isheld by the push stage 143. The semiconductor wafer 101 is held by thepush stage 143 at portions except for the peripheral edge thereof.

While the push stage 143 holds the semiconductor wafer, the top ringguides 148 are raised without being stopped, and the guide ring 301 isguided by the taper surfaces 208 of the top ring guides 148. The centerof the top ring guides 148 is aligned with the center of the top ring 32by the linear way 149 movable in X and Y directions, and the upper steps200 of the top ring guides 148 contact the lower surface of the guidering 301 and lifting of the guide stage 141 is stopped.

When the upper steps 200 of the top ring guides 148 contact the lowersurface of the guide ring 301, the guide stage 141 is fixed and is notraised anymore. However, the air cylinder 146 continues to be actuateduntil the stopper fixed to the rod of the air cylinder 146 contacts theshock absorber 156, and hence only the spline shaft 142 continues to beraised because the compression spring 152 is compressed, and the pushstage 143 is further raised. At this time, as shown in FIG. 34D, thepush stage 143 holds the semiconductor wafer 101 at portions except forthe peripheral edge of the semiconductor wafer 101, and transports thesemiconductor wafer 101 to the top ring 32. After the semiconductorwafer 101 contacts the top ring 32, the lifting stroke of the aircylinder 146 is absorbed by the compression springs 159 to therebyprotect the semiconductor wafer 101.

After the top ring 32 completes the attraction of the semiconductorwafer 101, the pusher starts to be operated and the guide stage 141 andthe push stage 143 are lowered to the position shown in FIG. 34A. Whenthe guide stage 141 is lowered, the guide stage 141 is centered by thetaper portion formed on the guide sleeve 153 and the taper portionformed on the center sleeve 154. When the lowering of the guide stage141 is completed, the operation of the loading of the semiconductorwafer is completed.

-   2) Unloading a semiconductor wafer

The semiconductor wafer 101 is transported by the top ring 32 to a waferunload position located above the pusher 30. When the wafer unload stageof the rotary transporter 27 is located above the pusher 30 and does nothold the semiconductor wafer, the guide stage 141 and the componentsassociated with the guide stage 141 are raised by the air cylinder 146,and the guide ring 301 of the top ring 32 is guided by the taperedsurfaces 208 of the top ring guides 148. The center of the top ringguides 148 is aligned with the center of the top ring 32 by the linearway 149, and the upper steps 200 of the top ring guides 148 contact thelower surface of the guide ring 301 and the lifting of the guide stage141 is stopped. The air cylinder 146 continues to be actuated until thestopper fixed to the rod of the air cylinder 146 contacts the shockabsorber 156. However, since the upper steps 200 of the top ring guides148 contact the lower surface of the guide ring 301 to cause the guidestage 141 to be fixed at this position, the air cylinder 146 pushes thespline shaft 142 together with the air cylinder 145 against urging forceof the compression spring 152, thus lifting the push stage 143. At thistime, as shown in FIG. 34E, the push stage 143 is not raised to aposition higher than the wafer holding portion of the lower steps 201 ofthe top ring guides 148. In this embodiment, the air cylinder 146 isarranged to be further actuated after the top ring guides 148 contactthe guide ring 301. The shock at this time is absorbed by the spring152.

After the lifting actuation of the air cylinder 146 is completed, thesemiconductor wafer 101 is removed from the top ring 32. At this time,the semiconductor wafer 101 is centered by the lower tapered surfaces207 of the top ring guides 148, and the semiconductor wafer 101 is heldby the lower steps 201 of the top ring guides 148 at the peripheral edgeof the semiconductor wafer 101. After the semiconductor wafer 101 isheld by the pusher, the pusher starts to be operated to lower the guidestage 141. While the guide stage 141 is lowered, the guide stage 141 iscentered by the guide sleeve 153 and the center sleeve 154. While theguide stage 141 is lowered, the semiconductor wafer 101 is transferredfrom the pusher 30 to the rotary transporter 27. When the lowering ofthe guide stage 141 is completed, the operation of the unloading of thesemiconductor wafer is completed.

According to the pusher having the structure shown in FIG. 33 and FIGS.34A through 34E, since the pusher 30 has a centering mechanism forcentering the main components of the pusher with respect to the top ring32, adjustment of the positional relationship between the pusher 30 andthe top ring 32 can be easily performed. The lifting stroke of the pushstage 143 is set to a position higher than the lower surface of the topring 32 by about 2 mm, and thus positioning in a vertical direction canbe easily performed. At this time, the shock of contact in the verticaldirection can be absorbed by the spring.

Top Ring

FIG. 35 is a side view with a partially cross-section showing the topring. The top rings 32 and 33 have the same structure, and only the topring 32 will be described.

The top ring 32 is held by the top ring head 31 so that the top ring 32can perform various motions including rotation, pressing, and swing. Thetop ring 32 comprises a top ring body 300 for holding an upper surfaceof the semiconductor wafer and pressing the semiconductor wafer againstthe polishing surface of the turntable, a guide ring 301 for retainingthe outer periphery of the semiconductor wafer, and a backing pad 302attached to the lower surface of the top ring body 300 and having acushioning function between the top ring 32 and the semiconductor wafer.The top ring body 300 is made of material having a rigidity such asceramics, and has a wafer holding surface which is formed to a flatfinish surface so that the entire surface of the semiconductor wafer canbe uniformly pressed against the polishing surface. However, the waferholding surface of the top ring body 300 may have a slightly concave orconvex surface depending on the kind of the semiconductor wafer to bepolished.

The guide ring 301 has an inner diameter slightly larger than thediameter of the semiconductor wafer so that the semiconductor wafer isinserted into the guide ring 301 and retained by the guide ring 301. Thetop ring body 300 has a plurality of through-holes 303 which are opentoward the wafer holding surface and an opposite surface to the waferholding surface. The clean air or nitrogen gas having a positivepressure is supplied to the semiconductor wafer held by the waferholding surface through the through-holes 303, and certain areas of thesemiconductor wafer can be selectively and locally pressed against thepolishing surface. Further, a negative pressure is developed in thethrough-holes 303, and the semiconductor wafer is attracted under vacuumwhen the semiconductor wafer is transported. Further, clean air ornitrogen gas is ejected toward the semiconductor wafer through thethrough-holes 303, whereby the semiconductor wafer can be removed fromthe top ring body 300. In this case, the wafer removing force isheighten by mixing pure water with the clean air or gas, thereby makingit possible to remove the semiconductor wafer reliably.

An attachment flange 304 is mounted on an upper surface of the top ring32. The attachment flange 304 has a hemispherical hole defined centrallyin an upper surface thereof. A drive flange 314 fixed to the top ringdrive shaft 91 is disposed above the attachment flange 304. The driveflange 314 also has a hemispherical hole defined therein. A ball 305which is hard and made of ceramics, for example, is provided in thehemispherical holes. A downward pressing force applied to the driveflange 314 is transmitted via the ball 305 to the attachment flange 304disposed therebelow.

On the other hand, the top ring head 31 supports the top ring 32 throughthe top ring drive shaft 91 comprising a spline shaft. The top ring head31 is supported by the support shaft 92. The support shaft 92 is rotatedby a motor (reference numeral 407 in FIG. 40) coupled to the lower endof the support shaft 92, and the top ring head 31 is swung by therotation of the support shaft 92. By this swing motion of the top ringhead 31, the top ring 32 can be moved to a polishing position, amaintenance position, and a transfer position. A motor 309 is providedabove the support shaft 92 and on the upper surface of the top ring head31, and a driving pulley 310 fixed to the end of the shaft of the motor309 is rotated by the motor 309 and a driven pulley 311 fixed to the topring drive shaft 91 is rotated through a belt 312. When the drivenpulley 311 is rotated, the top ring drive shaft 91 is rotated, and therotation of the top ring drive shaft 91 is transmitted to the top ring32, thus rotating the top ring 32.

Further, an air cylinder 313 is fixed to the upper surface of the topring head 31 in such a manner that the shaft of the air cylinder 313extends downwardly. The top ring head 31 and the shaft of the aircylinder 313 are coupled flexibly. By controlling air pressure suppliedto the air cylinder 313, the force for raising or lowering the top ringdrive shaft 91, i.e., the force for raising or lowering the top ring 32can be controlled. A tensile/compressive load-type cell 322 isinterposed in the junction between the air cylinder 313 and the top ringhead 31 for measuring a vertical thrust force generated by the aircylinder 313 fixed to the top ring head 31. Since this thrust force isequal to a force for pressing a semiconductor wafer, a feedback circuitmay be formed using the measured thrust force for the purpose ofcontrolling the force for pressing the semiconductor wafer. The body ofthe air cylinder 313 and the top ring drive shaft 91 comprising a splineshaft are coupled to each other such that the top ring drive shaft 91can be rotated. When the air cylinder 313 is operated vertically, thetop ring drive shaft 91 is simultaneously operated vertically. The topring drive shaft 91 has a vertical through hole defined therein, with atube (not shown) disposed in the vertical through hole. Since the topring drive shaft 91 and the top ring 32 are rotated, a rotary joint 316is mounted on the upper end of the tube. A vacuum, a gas such as N₂ orclean air and/or liquid such as pure water is supplied via the rotaryjoint 316 to the top ring body 300.

The top ring 32 having the above structure attracts the semiconductorwafer which has been transported to the pusher 30 under vacuum, andholds the semiconductor wafer in the guide ring 301 of the top ring 32.Thereafter, the top ring 32 is swung from the position above the pusher30 to the polishing surface on the turntable. After the top ring 32 ismoved to the position above the turntable, the top ring 32 is rotated ata given rotational speed, and then lowered by the air cylinder 313 tocontact the semiconductor wafer with the polishing surface on theturntable. When the top ring 32 is lowered to the upper surface of theturntable, a sensor 321 for detecting the lower end of the stroke of theair cylinder 313 is actuated to generate a signal indicating that thedownward movement of the air cylinder 313 is completed. In response tothe signal, the air cylinder 313 is supplied with air under a pressurecorresponding to a desired pressing load for thereby pressing the topring 32 against the turntable 34 to apply a pressing force to thesemiconductor wafer. At the same time, a vacuum line for developing anegative pressure to attract the semiconductor wafer is cut off. At thistime, depending on the type of the layer to be polished of thesemiconductor wafer, the negative pressure may remain developed, or avalve is operated to control the pressure of the gas to apply a positivepressure to the upper surface of the semiconductor wafer for therebycontrolling the polished profile of the semiconductor wafer. Thepressure at this time is applied only to the through holes 303 definedin the wafer holding portion of the top ring 32. Therefore, depending onwhich area of the semiconductor wafer the pressure is to be applied to,the diameters, number, and positions of the through holes 303 are variedto achieve a desired polished profile.

After a predetermined time of polishing, the top ring 32 holds thesemiconductor wafer under vacuum. Thereafter, the semiconductor wafer101 held by the top ring 32 is moved toward the outer periphery of theturntable 34 while the semiconductor wafer contacts the polishing clothon the turntable. Finally, the semiconductor wafer 101 projects from theouter periphery of the turntable 34 in such a manner that the center ofthe semiconductor wafer 101 is located on the turntable 34 and near theperiphery of the turntable 34 as much as possible and about 40% of thesurface of the semiconductor wafer projects from the turntable 34.Thereafter, the air cylinder 313 is actuated, and the top ring 32holding the semiconductor wafer 101 is raised. Depending on thepolishing cloth which is used, the surface tension between the slurry onthe polishing cloth and the semiconductor wafer may be stronger than theattractive force of the top ring, tending to leave the semiconductorwafer on the polishing cloth. In order to reduce the surface tension,the semiconductor wafer is allowed to project from the turntable andthen the top ring 32 is raised. If more than 40% of the surface area ofthe semiconductor wafer projects from the turntable, then the top ringwould be tilted, causing the semiconductor wafer to hit the edge of theturntable and hence to crack. It is therefore preferable for thesemiconductor wafer to project about 40% of its surface area from theturntable. In other words, it is essential that the center of thesemiconductor wafer is located on the turntable 34.

When lifting of the top ring 32 is completed, the sensor 320 detects thecompletion of the lifting action of the air cylinder 313. Thereafter,the top ring 32 starts to be swung, and is moved to the position abovethe pusher 30 and transfers the semiconductor wafer 101 to the pusher30. After the semiconductor wafer is removed from the top ring 32, acleaning liquid is supplied to the lower surface of the top ring 32 froma nozzle or nozzles located below the top ring 32, and the wafer holdingsurface of the top ring 32 and surrounding regions are cleaned. Thepurpose of supply of the cleaning liquid is to prevent the top ring frombeing dried until a next semiconductor wafer is transferred to the topring, and the supply of the cleaning liquid may be continued. Thecleaning liquid may be intermittently ejected from the nozzle to reducethe running cost. While the semiconductor wafer is being polished, thepolishing time is divided into a plurality of steps, and the pressingforce and rotational speed of the top ring and the method of holding thesemiconductor wafer can be changed in each of the steps. It is alsopossible to change the kind, amount, density, temperature, and supplytiming of the abrasive liquid that is used.

If the current supplied to the motor for rotating the top ring ismonitored during the polishing process, then the torque outputted by themotor can be calculated. When the polishing of a semiconductor waferreaches the end point, the friction between the semiconductor wafer andthe polishing cloth is changed. The end point of the polishing of thesemiconductor wafer may be detected on the basis of a change in thetorque of the motor. Similarly, the current supplied to the motor forrotating the turntable 34 may be monitored, a change in the torque maybe calculated, and the end point of the polishing of the semiconductorwafer may be detected on the basis of a change in the calculated torque.While a semiconductor wafer is polished, vibrations of the top ring aremeasured, and the end point of the polishing of the semiconductor wafermay be detected by detecting inflection points of the vibrationwaveform. Furthermore, an electrostatic capacitance may be measured todetect the end point of the polishing process. These four types ofdetection of the end point of the polishing process are based on adetermination from different surface irregularities or different surfacelayer qualities or the thickness of the remaining layer before and afterthe semiconductor wafer is polished. The surface of a polishedsemiconductor wafer may be cleaned, the amount of a material removedfrom the semiconductor wafer may be confirmed, insufficient polishingmay be confirmed, and then the semiconductor wafer may be polished againto make up for the insufficient polishing.

Dresser

FIGS. 36 and 37 are vertical cross-sectional views of dressers. FIG. 36shows a diamond dresser, and FIG. 37 shows a brush dresser. Since thedressers 38 and 39 are of substantially the same structure, only thedresser 38 will be described below.

As shown in FIG. 36, the dresser 38 has a dresser plate 370 having adressing surface for dressing the polishing cloth. The dresser plate 370is fastened to an attachment flange 375 which has a hemispherical holedefined centrally in an upper surface thereof. A drive flange 371 fixedto the dresser drive shaft 93 is disposed above the attachment flange375. The drive flange 371 also has a hemispherical hole defined therein.A ball 372 which is hard and made of ceramics, for example, is providedin the hemispherical holes. A downward pressing force applied to thedrive flange 371 is transmitted via the ball 372 to the dresser plate370. Diamond particles 373 for correcting the shape of the polishingcloth and dressing the polishing cloth are electrodeposited on a lowersurface of the dresser plate 370. Alternatively, a number of hardprotrusions of ceramics, for example, may be disposed on the dresserplate 370. The diamond particles or hard protrusions may be replacedonly by replacing the dresser plate 370 for thereby easily performingother types of dressing processes. In any case, since the surfaceconfiguration of the dresser plate 370 is reflected in the surfaceconfiguration of the polishing cloth that is dressed, the dressingsurface of the dresser is finished to a flat surface.

The dresser drive shaft 93 is supported on the dresser head 94 (see FIG.2). The dresser head 94 has essentially the same function as the topring head 31. The dresser drive shaft 93 is rotated by a motor andvertically moved by an air cylinder. The details of the structure of thedresser head 94 are substantially the same as those of the top ring head31, and will not be illustrated.

FIG. 37 shows the brush dresser having a brush 374 mounted on the lowersurface of the dresser plate 370 in place of the diamond particles 373.Other structural details of the brush dresser are essentially the sameas those of the diamond dresser shown in FIG. 36.

For correcting the shape of the polishing cloth or dressing thepolishing cloth, the dresser is angularly moved from a cleaning positionabove a dressing position on the turntable. Upon completion of theangular movement of the dresser, the dresser rotates at a desiredrotational speed, and is lowered by the air cylinder. When the dresseris brought into contact with the upper surface of the turntable, asensor associated with the air cylinder for detecting the lower end ofits stroke is actuated to generate a signal indicating that the dresser38 has touched the turntable. In response to the signal, the aircylinder applies a pressing force to the dresser 38 to dress thepolishing cloth on the turntable under the desired pressing force. Afterthe dresser 38 has dressed the polishing cloth for a desired period oftime, the air cylinder is operated to lift the dresser 38 away from theturntable. Thereafter, the dresser 38 is angularly moved to the cleaningposition in which the dresser 38 is submerged in a water container 43,43′ (see FIG. 1) and cleaned. Rather than being submerged in the watertank, the dresser may be cleaned by a spray ejected from a spray nozzle,or by being pressed against a brush provided on the bottom of the watertank and rotated. The water tank 43′ is associated with the dresser 39.

When the dresser 38 is submerged in the water container 43, the cleaningwater in the water container 43 may be vibrated by ultrasonic energy. Ifthe upper surface of the dresser 38 were placed in the cleaning water inthe water container 43, then when the dresser 38 is dried after beinglifted out of the water container 43, any ground-off material on thedresser 38 would be solidified and tend to drop onto the turntable in apolishing process, thus adversely affecting the polishing process.Therefore, only the lower surface of the dresser 38 may be submerged inthe cleaning water, and the upper surface thereof may be cleaned by aspray nozzle. At this time, droplets of the spray are liable to beapplied to the upper surface of the dresser 38. Such droplets of thespray are prevented from entering the dresser 38 by a water-resistantcap 376 and a V-ring 377 and also a labyrinth 378 comprising members 378a and 378 b. The cleaning liquid used for cleaning the dresser maycomprise pure water or a chemical liquid. The above structure of thedresser may be applied to the top ring 32 shown in FIG. 35 or thedresser 38 shown in FIG. 37. The dressing operation may be performedwhile the current supplied to the motor for rotating the dresser isbeing measured, and a certain reference value of the measured currentmay be used as a sign indicative of the end point of the process ofcorrecting the shape of the polishing cloth or dressing the polishingcloth.

Dressing of Second Turntable

As shown in FIGS. 1 and 2, in the polishing apparatus, there areprovided the second turntables 36 and 37 which are smaller in diameterthan the first turntables 34 and 35. These second turntables 36 and 37may be used to slightly scrape off the surface of semiconductor wafers,i.e., in a finish polishing process such as a buffing-off process. Thesecond turntables are dressed by respective dressers, i.e., the dressers48 and 49 shown in FIG. 1. These dressers 48 and 49 will be described indetail below. While these dressers are collectively referred to as thedressers 48 and 49 in FIGS. 1 and 2, a portion of a tip end thereof willbe described as a dresser 3000.

FIG. 38 is a vertical cross-sectional view showing the structure of thedresser, and FIG. 39 is a side elevational view of the turntable and thedresser. While the dressers 48 and 49 shown in FIGS. 1 and 2 havecircular plate facing the turntables, the dresser 3000 shown in FIGS. 38and 39 has a rectangular plate facing the turntable.

The dresser 3000 is retracted in a water container 3020 while asemiconductor wafer is being polished. After the polishing of thesemiconductor wafer is completed, the dresser 3000 is lifted by an aircylinder 3008. A mechanism for lifting and lowering the dresser 3000will be described below. The dresser 3000 is coupled to the dresserdrive shaft 96, which is splined, at an end of a brush fixing seat 3002with a drive flange 3019 interposed therebetween. The dresser driveshaft 96 has an upper end supported by a bearing 3006 housed in abearing case 3023 which is fastened to an air cylinder 3008 with abracket 3007 interposed therebetween. The air cylinder 3008 is fixed toa lower surface of an upper portion of a base 3009 to provide amechanism for transmitting vertical motion of the air cylinder 3008 tothe dresser 3000. A guide 3010 for guiding vertical linear motion of theair cylinder 3008 is mounted on the base 3009. A slider 3018 that islinearly movable relatively on the guide 3010 is mounted on the bracket3007 for guiding motion of the air cylinder 3008.

A rotary ball spline 3028 for guiding linear motion of vertical movablecomponents ranging from the air cylinder 3008 to the dresser 3000 ismounted on the dresser drive shaft 96. The rotary ball spline 3028comprises a spline ring 3029 and an outer flange ring 3030. The splinering 3029 guides linear motion of the dresser drive shaft 96, andtransmits rotary motion to the dresser drive shaft 96. The outer flangering 3030 supports the rotation of the spline ring 3029. A pulley 3005is mounted on the spline ring 3029. The pulley 3005, when rotated,rotates the spline ring 3029, whose rotation is transmitted to thedresser drive shaft 96.

When the dresser 3000 reaches an elevated position, a sensor 3021 fordetecting the arrival of the dresser 3000 at the elevated positiongenerates a signal. Thereafter, the dresser 3000 and the dresser head 97are angularly moved to a dressing start position by a swinging mechanismwhich comprises an air cylinder 3016, a crank 3017 for converting linearmotion of the air cylinder 3016 to rotary motion, and a hollow rotatablesupport shaft 98 coupled to the dresser head 97 and rotatable by therotary motion of the crank 3017. Thus, the swing mechanism converts thelinear motion of the air cylinder 3016 to the rotary motion of thehollow rotatable support shaft 98 through the crank 3017.

When the dresser 3000 reaches a dressing position, a terminal sensor3024 mounted on the air cylinder 3016 generates a signal, and then thedresser 3000 is rotated about the dresser drive shaft 96. The dresser3000 is rotated as follows: A rotatable shaft 3013 inserted in thehollow rotatable support shaft 98 is connected to a motor 3014. When themotor 3014 is energized, the rotatable shaft 3013 is rotated. Therotatable shaft 3013 is supported by bearings 3032 disposed onrespective opposite ends of the hollow shaft 98. When the rotatableshaft 3013 is rotated by the motor 3014, a pulley 3011 mounted on theupper end of the shaft 3013 is rotated, and the rotation of the pulley3011 is transmitted via a timing belt 3012 to the pulley 3005. Therotation of the pulley 3005 is transmitted via the spline ring 3029 tothe dresser drive shaft 96.

If the motor 3014 detects when the rotational speed of the dresser 3000becomes steady, then the air cylinder 3008 lowers the dresser driveshaft 96 for the dresser 3000 to start dressing the polishing cloth. Ifa sensor 3022 for detecting the arrival of the dresser 3000 at a loweredposition does not generate a signal, then it is determined that thedresser 3000 has not reached the proper lowered position, and an erroris indicated. While the polishing cloth is being dressed, it is possibleto introduce a liquid such as pure water or a chemical liquid from adressing liquid supply port 3031 onto the turntable 36.

After the dressing process, the dresser 3000 is lifted. After the sensor3021 for detecting the arrival of the dresser 3000 at the elevatedposition generates a signal, the rotation of the dresser 3000 isstopped. After the motor 3014 has confirmed the stoppage of therotation, the dresser 3000 is angularly moved to a standby position.After a terminal sensor 3025 of the air cylinder 3016 generates asignal, the dresser 3000 is lowered into the water container 3020. Now,a series of dressing operation is finished.

The polishing cloth and the fixed abrasive grain plate (or a grindingstone) are replaceable. A brush body 3001 and the diamond dresser arealso replaceable. The dresser 3000 comprises the brush body 3001 and thebrush fixing seat 3002. The brush body 3001 is replaceable as anexpendable element.

The rotatable shaft 98 and the rotary ball spline 3028 are associatedwith respective protective outer casings 3026 and 3027 each comprising alabyrinth mechanism for preventing liquids including pure water, aslurry and a chemical liquid from entering the interior of theprotective outer casings 3026 and 3027 while the dresser 3000 is in use.

The portion of the dresser 3000 which faces the turntable is of anelongated shape. Since the dresser 3000 is slender and the rotatableshaft is positioned at an end thereof, the dresser 3000 has a smalleroccupied area and an equivalent dressing area as compared with circulardressers.

Turntable

FIG. 40 is a front view of the turntable. The turntables 34 and 35 aredisposed in the areas C and D, respectively. Depending on the polishingprocesses, in order to improve processing capability of two-stagepolishing, the small-sized turntables 36 and 37 may be provided in theareas C and D, respectively as shown in FIG. 1. The polishing tables 34,35, 36 and 37 may comprise two kinds of turntables, i.e. a rotating-typeturntable and a scroll-type turntable. Both types can be incorporated inthe same area, and various polishing processes can be selected.

The turntable shown in FIG. 40 comprises the rotating-type turntable.The rotating-type turntable 34 has a polishing surface whose radius islarger than the diameter of the semiconductor wafer, the turntable 34and the semiconductor wafer are rotated in the same direction, and thesemiconductor wafer is polished at the position spaced from the centerof the turntable. In this manner, the relative velocity between thesemiconductor wafer and the turntable can be equal at any point on thesemiconductor wafer, if the turntable 34 and the semiconductor wafer arerotated at the same rotational speed.

As shown in FIG. 40, the turntable 34 is directly driven by a motor 401,and has such a structure that thrust and radial shaft loads thereof aresupported by bearings of the motor 401. The motor 401 is accommodated ina motor housing 402 which is integral with a housing 403 that houses aswing shaft for angularly moving the top ring and a motor housing 404that houses a swing shaft for angularly moving the dresser. The motorhousing 402 may be directly mounted on a base which supports thepolishing apparatus in its entirety or may be integral with such a base.The motor 401 has a hollow rotor with a plurality of pipes passingtherethrough. The pipes in the hollow rotor are connected to a rotaryjoint 405 connected to the lower end of the hollow rotor.

The hollow rotor has a mechanism which can operate in synchronism withthe rotation of the hollow rotor. An encoder 406 is coupled to themechanism for measuring the rotational speed of the motor 401 at alltimes. A signal indicative of the measured rotational speed is suppliedto a driver which controls the motor 401 for thereby enabling the motor401 to rotate at a proper rotational speed. The end point of a polishingprocess can be detected by monitoring a current of the motor 401. Themotor 401 has a stator case having a passage defined therein to allow amotor coolant to pass therethrough so that the motor 401 is continuouslyoperated under a high load.

The turntable 34 may have a sensor for optically detecting an abnormalcondition such as dislodgement of a semiconductor wafer from the topring 32. When such an abnormal condition occurs, the motor 401 canimmediately stop the turntable 34 in response to a signal from thesensor.

The turntable 34 and the motor 401 are detachably installed in thepolishing apparatus. The turntable 34 may be of either the type in whicha polishing cloth is attached to the turntable 34 or the type in which apolishing cloth is attached to a cartridge that can be removably mountedon the turntable 34. Whichever type the turntable 34 may be of, theturntable 34 has a surface plate which may be of either a flat, convex,or concave shape. If the turntable 34 is of the former type, then apolishing cloth is attached to the surface plate of the turntable 34. Ifthe turntable 34 is of the latter type, then a polishing cloth or afixed abrasive grain plate (grinding stone) is attached to thecartridge. If the turntable 34 is of the former type, then the surfaceplate may be made of stainless steel or ceramics. If the turntable 34 isof the latter type, then the surface plate shape, the polishing cloth,or the fixed abrasive grain plate may be changed simply by replacing thecartridge. If a cartridge type surface plate with a polishing clothattached thereto is available for ready use, then the time required forreplacing the polishing cloth on the surface plate can be shortened. Thecartridge type surface plate may be of either a solid structure or ahollow honeycomb structure for reduced weight. The cartridge typesurface plate of the hollow honeycomb structure can reduce the burden onthe operator for cartridge replacement.

Turntable Cooling and Temperature Adjustment

The surface plate has in its lower portion a mechanism for adjusting thetemperature of the surface plate. Temperature adjustment water issupplied through a pipe in the hollow shaft of the motor 401 to a tablecooling chamber in the lower portion of the surface plate. The tablecooling chamber has coolant passages disposed therein for uniformlycooling the entire surface of the turntable. The layout of the coolantpassages differs depending on the surface plate that is used.

A pipe for supplying the temperature adjustment water to the polishingapparatus is combined with a temperature sensor. When the temperature ofthe temperature adjustment water deviates from an allowable range withrespect to a preset temperature, the process is interlocked. A signalindicative of the detected temperature may be supplied to a temperatureadjustment water control unit outside of the polishing apparatus forfeedback control. The pipe for supplying the temperature adjustmentwater is also combined with a flow rate meter and a pressure gage, sothat the process can be interlocked when the temperature adjustmentwater is supplied at an abnormal flow rate or under an abnormalpressure. A flow regulating valve and a pressure regulator are alsoprovided for controlling the flow rate and the pressure of thetemperature adjustment water within the polishing apparatus. Accordingto another temperature control process, the temperature of the polishingsurface on the turntable 34 is measured by a noncontact type temperaturesensor, and a signal indicative of a measured temperature is sent to thetemperature adjustment water control unit to perform feedback control.

Next, the turntable other than the turntable shown in FIG. 40 will bedescribed.

Scroll-type Turntable

FIG. 41 is a cross-sectional view showing the scroll-type secondpolishing turntable, FIG. 42A is a cross-sectional view taken along lineP—P of FIG. 41, and FIG. 42B is a cross-sectional view taken along lineX—X of FIG. 42A.

The scroll-type second turntable 36 has an upper flange 1751 of a motor1750, and a hollow shaft 1752 connected to the upper flange 1751 bybolts. A set ring 1754 is supported by the upper portion of the shaft1752 through a bearing 1753. A table 1759 is fixed to the set ring 1754,and a polishing table 1755 is fixed to the table 1759 by bolts 1790. Thepolishing table 1755 may comprise a grinding stone (fixed abrasiveplate) entirely, or may comprise a plate made of a corrosion-resistantmetal such as stainless steel and a polishing cloth attached to theplate. In case of using the grinding stone or the polishing cloth, thepolishing table 1755 may have a flat upper surface or a slightly convexor concave upper surface. The shape of the upper surface of thepolishing table 1755 is selected depending on the kind of thesemiconductor wafer 101 to be polished. The outer diameter of thepolishing table 1755 is set to a diameter having the diameter of thesemiconductor wafer plus distance 2 e (described below) or larger. Thatis, the diameter of the polishing table 1755 is arranged such a diameterthat when the polishing table 1755 makes a translational motion, thesemiconductor wafer does not project from the outer periphery of thepolishing table 1755. The translational motion may be called scrollmotion or orbital motion.

The set ring 1754 has three or more supporting portions 1758 in acircumferential direction, and the table 1759 is supported by thesupporting portions 1758. A plurality of recesses 1760, 1761 are formedat positions corresponding to the upper surface of the supportingportions 1758 and the upper end of the cylindrical member 1795 atangularly equal intervals in a circumferential direction, and bearings1762 and 1763 are mounted in the recesses 1760 and 1761. As shown inFIGS. 41 and 42, a support member 1766 having two shafts 1764 and 1765whose central axes are spaced by “e” is supported by the bearings 1762and 1763. Specifically, the two shafts 1764 and 1765 are inserted intothe bearings 1762 and 1763, respectively. Thus, the polishing table 1755makes a translational motion along a circle having a radius “e” by themotor 1750.

Further, the center of the shaft 1752 is off-centered by “e” from thecenter of the motor 1750. A balancer 1767 is fixed to the shaft 1752 forproviding a balance to the load caused by eccentricity. The supply ofthe abrasive liquid onto the polishing table 1755 is conducted throughthe insides of the motor 1750 and the shaft 1752, a through-hole 1757provided at the central portion of the table 1759, and a coupling 1791.The supplied abrasive liquid is once stored in a space 1756 definedbetween the polishing table 1755 and the table 1759, and then suppliedto the upper surface of the polishing table 1755 through a plurality ofthrough-holes 1768 formed in the polishing table 1755. The number andposition of the through-holes 1768 can be selected depending on the kindof processes. In the case where the polishing cloth is attached to thepolishing table 1755, the polishing cloth has through-holes at positionscorresponding to the positions of the through-holes 1768. In the casewhere the polishing table 1755 is made of a grinding stone in entirety,the upper surface of the polishing table 1755 has grid-like, spiral, orradial grooves, and the through-holes 1768 may communicate with suchgrooves.

The supplied abrasive liquid may be selected from pure water, chemicals,or slurry, and, if necessary, more than one kind of the abrasive liquidcan be supplied simultaneously, alternatively, or sequentially. In orderto protect a mechanism for performing a translational motion from theabrasive liquid during polishing, a flinger or a thrower 1769 isattached to the table 1759, and forms a labyrinth mechanism togetherwith a trough 1770.

In the turntable having the above structure, the upper and lowerbearings 1762, 1763 are axially interconnected by the support member1766 comprising a cranked joint having the upper and lower shafts 1764,1765 that are fitted respectively in the upper and lower bearings 1762,1763. The shafts 1764, 1765 and hence the upper and lower bearings 1762,1763 have respective axes horizontally spaced from each other by adistance “e”. The cylindrical member 1795 for supporting the lowerbearing 1763 is fixed to the frame, and hence is stationary. When themotor 1750 is energized, the shaft 1752 is rotated by the radius ofgyration (e) about the central axis of the motor 1750, and thus thepolishing table 1755 makes a circulatory translational motion (scrollmotion) through the cranked joint, and the semiconductor wafer 101attached to the top ring 32 is pressed against a polishing surface ofthe polishing table 1755. The semiconductor wafer 101 is polished by theabrasive liquid supplied through the through-hole 1757, the space 1756and the through-holes 1768. The semiconductor wafer 101 is polished bythe relative circulatory translational motion having a radius “e”between the polishing surface of the polishing table 1755 and thesemiconductor wafer 101, and the semiconductor wafer 101 is uniformlypolished over the entire surface of the semiconductor wafer. If asurface, to be polished, of the semiconductor wafer 101 and thepolishing surface have the same positional relationship, then thepolished semiconductor wafer is affected by a local difference in thepolishing surface. In order to eliminate this influence, the top ring 32is rotated at a low speed to prevent the semiconductor wafer from beingpolished at the same area on the polishing surface.

Overhang-type Turntable

FIG. 43 is a cross-sectional view of the overhang-type second turntable.The overhang-type second turntable 36 has a plate 1700 coupled to amotor 1705 through a flange 1704. The plate 1700 is rotated by the motor1705. The rotational speed of the plate 1700 is measured by counting thenumber of times in which a dog 1707 attached to the plate 1700 passesthrough a proximity switch 1708, and is indicated. The overhang-typeturntable is protected from the slurry or pure water used for polishingor dressing by a labyrinth 1701, O-rings 1702 and 1703, and a secondlabyrinth 1710 provided inside of the labyrinth 1701. A vent port 1709is formed in the housing 1706 so that high load polishing, or continuouspolishing for a long period of time can be performed. That is, heat inthe gap between the housing 1706 and the motor 1705 is discharged fromthe vent port 1709, and the load of the motor 1705 is reduced.

The overhang-type turntable has its center located in the diameter ofthe semiconductor wafer to be polished. By rotating the semiconductorwafer and the turntable in the same direction, the relative velocity ofthe semiconductor wafer and the turntable is equal at any point on thesemiconductor wafer. The plate 1700 is disposed on the upper surface ofthe turntable, and a polishing cloth or a grinding stone may be attachedto the plate 1700. The abrasive liquid, chemicals, or water can besupplied to the plate 1700 from a nozzle or nozzles located above theplate 1700.

Abrasive Liquid Supply Nozzle

An abrasive liquid supply nozzle is a device for supplying an abrasiveliquid to the polishing surface such as the polishing cloth on theturntable.

FIGS. 44A, 44B, and 45 show the abrasive liquid supply nozzle. FIG. 44Ais a plan view of the abrasive liquid supply nozzle, FIG. 44B is a sideelevational view, partly in cross section, of the abrasive liquid supplynozzle, and FIG. 45 is a plan view showing the position of the abrasiveliquid supply nozzle 40 with respect to the turntable 34.

As shown in FIG. 45, the abrasive liquid supply nozzle 40 can move to asupply position F for supplying the abrasive liquid onto the turntable34, a first retracted position E, and a second retracted position D. Theabrasive liquid supply nozzle 40 rotates about a rotatable shaft 3051 tobring the tip end of a hollow liquid supply arm 3050 to one of thepositions.

A mechanism for rotating the abrasive liquid supply nozzle 40 will bedescribed below.

The rotatable shaft 3051 is rotated when a swing arm 3052 attached tothe lower end of the rotatable shaft 3051 is angularly moved about theaxis of the rotatable shaft 3051. The swing arm 3052 and air cylinders3053 and 3054 jointly constitute a link mechanism. When rods of the aircylinders 3053 and 3054 are extended and contracted linearly, the swingarm 3052 is angularly moved to rotate the rotatable shaft 3051 that ispositioned at the center of rotation of the swing arm 3052. The aircylinder 3054 is fixed to a cylinder bracket 3056 fixed to a base 3055.The air cylinder 3053 is connected by a pin to the tip end of the rod ofthe air cylinder 3054 such that the air cylinder 3053 can rotate withrespect to the end of the rod of the air cylinder 3054. The rotatableshaft 3051 is rotatably supported by bearings 3057 housed in a bearingcase 3058.

Operation of the two air cylinders 3053 and 3054 will be describedbelow.

When the tip end of the liquid supply arm 3050 is positioned over theturntable 34, e.g., at the center of the turntable 34, the rod of theair cylinder 3053 is extended, and the rod of the air cylinder 3054 iscontracted. At this time, a position sensor 3066 of the air cylinder3053 and a position sensor 3068 of the air cylinder 3054 generaterespective signals. If such signals are not generated, then a controlcomputer determines that the abrasive liquid supply nozzle 40 is not ina normal position, displays an error, and interlocks the process.

When the tip end of the liquid supply arm 3050 is located in theposition E, both the rods of the air cylinders 3053 and 3054 arecontracted. At this time, a position sensor 3067 of the air cylinder3053 and the position sensor 3068 of the air cylinder 3054 generaterespective signals for the control computer to recognize the position ofthe abrasive liquid supply nozzle 40.

When the tip end of the liquid supply arm 3050 is located in theposition D, the rod of the air cylinder 3053 is contracted, and the rodof the air cylinder 3054 is extended. At this time, the position sensor3067 of the air cylinder 3053 and a position sensor 3069 of the aircylinder 3054 also generate respective signals for the control computerto recognize the position of the abrasive liquid supply nozzle 40.

Next, a sensor 3064 attached to the liquid supply arm 3050 will bedescribed below.

When a scattering prevention cover 3070 around the turntable 34 isinstalled in a normal position, the sensor 3064 senses a dog 3065mounted on the scattering prevention cover 3070 directly below thesensor 3064, and generates a signal. Therefore, a failure to install thescattering prevention cover 3070 or a positional misalignment of thescattering prevention cover 3070 can easily be detected. Specifically,the scattering prevention cover 3070 is vertically movable, and islowered when the turntable 34 is inspected and serviced for maintenance.If a semiconductor wafer were polished on the turntable 34 with thescattering prevention cover 3070 being lowered, then the abrasive liquidwould be scattered around. Because of a signal generated by the sensor3064, the motor for rotating the turntable 34 is prevented from beingenergized in error, and hence the abrasive liquid is prevented frombeing scattered around.

The liquid supply arm 3050 has an arm body 3059 on which a flinger 3060is mounted as a protective mechanism for protecting a mechanism forrotating the rotatable shaft 3051 against liquids including an abrasiveliquid, a chemical liquid, pure water, etc. The flinger 3060 and apolisher pan 3061 jointly constitute a labyrinth mechanism.

Operation of the liquid supply arm 3050 will be described below.

In the liquid supply position F, four tubes 3063 in the liquid supplyarm 3050 are positioned in alignment with the center of rotation of theturntable 34, and one of the four tubes 3063 discharges the abrasiveliquid. The discharged abrasive liquid drops onto the center of theturntable 34, spreads uniformly over the entire surface of the turntable34 to thus cover the polishing surface thereon. The tubes 3063 areinserted in the hollow liquid supply arm 3050, and fixed thereto by afixing member 3062 to direct the tip ends of the tubes 3063perpendicularly to the turntable 34.

When the polishing surface is dressed, one of the four tubes 3063discharges the dressing liquid. The discharged dressing liquid alsodrops perpendicularly onto the center of the turntable 34 and spreadsuniformly over the entire polishing surface of the turntable 34.

With the liquid supply arm 3050, therefore, a liquid discharged from anyof the tubes 3063 is supplied perpendicularly to the center of theturntable 34 exactly at the desired position on the polishing surface onthe turntable 34.

Rather than directing the tip ends of the tubes 3063 perpendicularlydownwardly toward the turntable 34, liquids can be suppliedperpendicularly to the turntable 34 by regulating the flow rates of theliquids with flow rate regulating valves V₁ and V₂ disposed betweenliquid tanks T₁ and T₂ and the tubes, such that the liquids dischargedfrom the tip ends of the tubes 3063 immediately flow perpendicularly tothe turntable 34.

For replacing the polishing cloth on the turntable 34, the liquid supplyarm 3050 is angularly moved to the first retracted position E by thelink mechanism including the two air cylinders 3053 and 3054. Since theliquid supply arm 3050 is no longer present over the turntable 34, thepolishing cloth thereon can easily be replaced. At this time, the tipends of the tubes 3063 at the tip end of the liquid supply arm 3050 arepositioned directly above a recess 3071 in the scattering preventioncover 3070. Any liquids discharged from the tubes 3063 at this time dropthrough the recess 3071 into a container positioned therebelow, and donot contaminate components surrounding the turntable 34.

The tubes 3063 may be connected to a source of pure water and cleaned bypure water flowing therethrough without contaminating surroundingcomponents.

If a maintenance process that cannot be performed at the positions E andF, e.g., a process for measuring the rate of a discharged liquid or aprocess of inspecting components around the turntable is needed, thenthe liquid supply arm 3050 is moved to the second standby position D bythe link mechanism. Since the liquid supply arm 3050 is no longerpositioned above the turntable 34 and the scattering prevention cover3070, the above maintenance process can easily be carried out.

In the above embodiment, the liquid supply arm 3050 is selectivelystopped in the three positions by the link mechanism including the aircylinders 3053 and 3054, and the liquid supply arm 3050 may be stoppedin at least one liquid supply position and at least one retractedposition.

FIGS. 46 through 48 show various abrasive liquid supply systems.

The polishing apparatus has a plurality of polishing surfaces to which aplurality of slurries or abrasive liquids can be supplied. There are aplurality of abrasive liquid supply systems including a system forstably supplying an abrasive liquid at a flow rate required for apolishing process from an external source, a system for supplying anabrasive liquid under a pressure which is not controlled at a constantlevel, at a flow rate which is not controlled at a constant level, and asystem for drawing an abrasive liquid from an abrasive liquid tankinstalled outside of the polishing apparatus. If the abrasive liquid issupplied stably, then as shown in FIGS. 46 and 47, three-way valves areconnected to primary inlet ports of supply lines for the abrasiveliquid, and when no abrasive liquid is to be supplied to the polishingsurface, a valve 420 out of the three-way valves is closed, and a valve421 out of the three-way valves is opened to return the abrasive liquidoutside of the polishing apparatus for circulation. When the abrasiveliquid is to be supplied to the polishing surface, the valve 420 isopened and the valve 421 is closed.

In addition to the valves, pressure sensors are provided in the supplylines for the abrasive liquid to monitor the pressure of the abrasiveliquid. If the pressure of the abrasive liquid is too high or noabrasive liquid is supplied, the detected pressure is used to interlockthe process. Constant-rate valves may be provided downstream of theabove valves for precisely controlling the flow rate of the abrasiveliquid supplied to the polishing surface at positions near the polishingsurface. The system may be constructed to control the constant-ratevalves with electric signals to vary the flow rates of the abrasiveliquid through the constant-rate valves, so that the flow rate of thesupplied abrasive liquid may be varied each time a semiconductor waferis polished, or a semiconductor wafer is polished in a stepwise mannerby combining various rotational speeds and various flow rates.

After the polishing process, pure water may be supplied instead of theabrasive liquid to polish or clean the semiconductor wafer. Thus, purewater lines are provided to supply such pure water. The timing of supplyof the pure water is controlled by opening and closing a valve 426. Thepure water lines may be used to supply pure water to the polishingsurface when the polishing cloth is to be dressed.

If the flow rate of the abrasive liquid to be supplied is not constantor the abrasive liquid is drawn from the tank disposed outside of thepolishing apparatus, then as shown in FIG. 48, pumps 430 and 432 areprovided in supply lines for the abrasive liquid. The pumps 430 and 432should preferably comprise tubing pumps that are often used as medicalequipment because they are small in size and can conveniently be used.The pumps 430 and 432 are effective to make the flow rate of thesupplied abrasive liquid constant, vary the flow rate of the suppliedabrasive liquid each time a semiconductor wafer is polished, or polish asemiconductor wafer in a stepwise manner by combining various rotationalspeeds and flow rates at different stages.

In order to mix two or more kinds of abrasive liquid or dilute theabrasive liquid with pure water immediately before the abrasive liquidis supplied to the polishing surface, valves 440 and 441 maybe added asshown in FIG. 46. Constant-rate valves and pressure sensors may beincorporated in lines connected to these valves 440 and 441 forsupplying the abrasive liquid at a freely varied concentration.

All the systems shown in FIGS. 46 through 48 include a flushing line andvalves 424, 425 for removing any remaining abrasive liquid from theabrasive liquid supply lines with pure water so that such remainingabrasive liquid will not be dried and solidified. The valves 424 and 425may be opened for a certain period of time to clean the supply lineseach time the process of polishing a semiconductor wafer is finished, orat certain intervals while the polishing apparatus is waiting for a nextprocess to begin.

Cleaning of the Semiconductor Wafer

FIG. 32 is a schematic view showing a cleaning operation of thesemiconductor wafer and various devices for handling the semiconductorwafer. The semiconductor wafers which are transported by the rotarytransporter 27, the pushers 30 and 30′, the lifters 29 and 29′, the toprings 32 and 33, and the reversing devices 28 and 28′ are cleaned duringtheir transportation conducted after polishing. The semiconductor waferto which the abrasive liquid and the ground-off particles are attachedduring polishing is cleaned in an early stage, and unnecessary etchingor oxidization by chemical component in the abrasive liquid isprevented. If the abrasive liquid or the ground-off particles are driedon the semiconductor wafer to adhere to the semiconductor wafer firmly,then they are difficult to be removed by cleaning. Thus, thesemiconductor wafer is required to be transported to the cleaningapparatuses without being dried. The five units for transporting thesemiconductor wafer are also required to be cleaned because they contactdirty semiconductor wafers.

The pusher 30 and 30′ transport the semiconductor wafers between the toprings 32 and 33 and the rotary transporter 27, respectively. Thesemiconductor wafer to be polished is transported to the position abovethe pusher 30 or 30′ by the rotary transporter 27. The pusher 30 or 30′transports the semiconductor wafer to the top ring 32 or 33. Thesemiconductor wafer which has been polished is transported form the topring 32 or 33 to the rotary transporter 27 through the pusher 30 or 30′.The semiconductor wafer which has been polished has the abrasive liquidor the ground-off particles attached thereto, and hence the abrasiveliquid or the ground-off particles tend to be attached to the pusher 30or 30′. Therefore, if the pusher is not cleaned, the pusher contaminatessubsequent semiconductor wafers to be polished. Further, if the pusheris not cleaned and is left as it is for a long period of time, theabrasive liquid or the ground-off particles are solidified to form largegrains and such grains are attached to the semiconductor wafer. If thesemiconductor wafer is polished in this state, the semiconductor waferis damaged due to the attached grains. Therefore, it is necessary toclean the pusher 30 or 30′, especially the stage of the pusher 30 or 30′for placing the semiconductor wafer thereon.

As shown in FIG. 32, a cleaning liquid such as pure water, chemicals,ionic water or ozone water is ejected from the spray nozzles 1500. Thecleaning is performed by ejecting the cleaning liquid from the nozzles1500, after the semiconductor wafer 101 which has been polished isreceived by the pusher 30 or 30′, lowered, and then transferred to therotary transporter 27 and further lowered until receiving a signalindicative of completion of lowering the pusher 30 or 30′ from a sensor.

The rotary transporter 27 holds the semiconductor wafer thereon andtransports the semiconductor wafer by its rotation between the transferposition with the lifter 29 or 29′ and the transfer position with thepusher 30 or 30′. In the transfer of the semiconductor wafer afterpolishing, the semiconductor wafer to which the abrasive liquid or theground-off particles are attached is transported, and hence the pins 201and therearound are contaminated by the abrasive liquid or theground-off particles. The semiconductor wafer which has been polished istransferred onto the pins 201 on the rotary transporter 27 by way of thepusher 30 or 30′. After the semiconductor wafer is transferred to therotary transporter 27, a cleaning liquid such as pure water, chemicals,ionic water, or ozone water is supplied to the upper and lower surfacesof the semiconductor wafer to clean both surfaces of the semiconductorwafer. The spray nozzles 1501, 1502, 1503 and 1504 fixed to the polisherpans 80 and 80′ or the partition wall 24 are used to supply the cleaningliquid, and the semiconductor wafer can be cleaned under a desired flowrate and a desired pressure of the cleaning liquid, and a desired angleof the nozzle. The cleaning of the upper and lower surfaces of thesemiconductor wafer is simultaneously conducted, and an air operatingvalve for supplying a cleaning liquid may be shared. In this case, apipe is branched at the downstream side of the outlet of the airoperating valve, and the cleaning liquid from the branched pipes may besupplied to the upper and lower surfaces of the semiconductor wafer.Further, since the pattern surface of the semiconductor wafer facesdownwardly, yield of the semiconductor wafer is improved if the lowersurface of the semiconductor wafer is more intensively cleaned than theupper surface thereof.

Therefore, it is desirable that the nozzle for supplying to the lowersurface of the semiconductor wafer can flow a larger amount of cleaningliquid than the nozzle for supplying to the upper surface of thesemiconductor wafer, or the diameter of the pipe for supplying thecleaning liquid to the lower surface of the semiconductor wafer islarger than that of the pipe for supplying the cleaning liquid to theupper surface of the semiconductor wafer. It may also be possible thattwo air operating valves are discretely used for the upper surface andthe lower surface of the semiconductor wafer.

Further, when the rotary transporter 27 does not hold the semiconductorwafer, the wafer support pins 201 may be cleaned by the above nozzle forcleaning the semiconductor wafer.

The lifters 29 and 29′ transport the semiconductor wafer between thereversing device 28 and 28′ and the rotary transporter 27, respectively.The semiconductor wafer to be polished is transferred to the reversingdevice 28 or 28′ by the robot. The lifter 29 or 29′ transfers thesemiconductor wafer from the reversing device 28 or 28′ to the rotarytransporter 27. The semiconductor wafer which has been polished istransported by the rotary transporter 27 to the position above thelifter 29 or 29′, and the semiconductor wafer is transferred to thereversing device 28 or 28′ by the lifter 29 or 29′. The semiconductorwafer which has been polished is cleaned on the rotary transporter 27 sothat the abrasive liquid or the ground-off particles may be removed.However, this cleaning is not sufficient to remove the abrasive liquidor the ground-off particles entirely, and thus the lifter 29 or 29′which transports the semiconductor wafer may be contaminated. Therefore,the stage 260 (see FIG. 30) for placing the semiconductor wafer thereonis required to be cleaned in the intervals between the transfer of thesemiconductor wafer. In this case, the cleaning liquid such as purewater or chemicals may be sprayed from the spray nozzle 1505.Particularly, it is effective to start cleaning of the polishedsemiconductor wafer 101 when the semiconductor wafer is transferred tothe reversing device 28 or 28′, the lifter 29 or 29′ is lowered, andthen the sensor 267 issues a signal indicative of the completion oflowering of the lifter 29 or 29′.

The top rings 32 and 33 are contaminated by the abrasive liquid or theground-off particles in each polishing. Therefore, it is necessary thatthe top rings 32 and 33 are cleaned after removing the polishedsemiconductor wafer therefrom and before receiving a subsequentsemiconductor wafer to be polished. After the semiconductor wafer isremoved from the top ring 32 or 33, the wafer holding surface 32 a or 33a is exposed. The wafer holding surface 32 a or 33 a is cleaned toremove the abrasive liquid or the ground-off particles before polishingthe subsequent semiconductor wafer, thereby preventing the abrasiveliquid or the ground-off particles from entering between the waferholding surface 32 a or 33 a and the semiconductor wafer. As shown inFIG. 32, the cleaning liquid such as pure water, chemicals, ionic water,or ozone water is supplied from the spray nozzle 1506 to the waferholding surface 32 a or 33 a. Further, before the semiconductor waferwhich has been polished is removed from the top ring 32 or 33 andtransferred to the pusher 30 or. 30′, the pattern surface of thesemiconductor wafer may be cleaned by the cleaning liquid supplied fromthe nozzle 1506.

The reversing devices 28 and 28′ reverse a semiconductor wafer duringthe transfer between the robot 20 and 21 and the lifter 30 and 30′,respectively. Since the polished semiconductor wafer is subjected toonly a simple cleaning operation before it is transported to thereversing device 28 or 28′, while the semiconductor wafer stays in thereversing device 28 or 28′, the cleaning liquid such as pure water,chemicals, ionic water, or ozone water is supplied to the semiconductorwafer from the spray nozzles 1507 and 1508. After the polishedsemiconductor wafer is transferred to the reversing device and reversedthereby, the semiconductor wafer faces the pattern surface upwardly. Thereversed semiconductor wafer waits for the robot to which it will betransferred. In some cases, the reversed semiconductor wafer waits forthe robot for a long period of time depending on processing time forpolishing or cleaning. In such cases, the supply of the cleaning liquidis mainly to prevent the semiconductor wafer from being dried. Among thecleaning apparatuses 5, 6, 22 and 23, in the case where the cleaningtime in one or more cleaning apparatuses is extremely longer than thepolishing time, the semiconductor wafer 101 may stay in the stages 211or 213 (see FIG. 31) on the rotary transporter 27. In this case also,the spray nozzles 1503 and 1504 may be used for supplying the cleaningliquid for preventing the semiconductor wafer on the rotary transporter27 from being dried.

In the above, the cleaning in the rotary transporter and the variousunits around the rotary transporter has been described. In summary, thesemiconductor wafer which has been polished is cleaned in the followingsequence:

-   1) cleaning on the top ring 32 or 33-   2) cleaning on the rotary transporter 27-   3) cleaning in the reversing device 28 or 28′

In order to prevent the semiconductor wafer from being subjected tounnecessary etching or oxidization by the abrasive liquid, it isdesirable that the cleaning by chemicals is conducted immediately aftercompleting the polishing of the semiconductor wafer. Therefore, it ismore effective to clean the semiconductor wafer on the top ring or therotary transporter by chemicals than pure water.

In contrast thereto, cleaning in the reversing device is conducted forpreventing the semiconductor wafer from being dried rather thancleaning, because the semiconductor wafer is cleaned beforehand to somedegree.

Therefore, if semiconductor wafers are cleaned on the top ring and therotary transporter with chemicals, and in the reversing device with purewater, then the semiconductor wafers can be cleaned optimally at aminimized cost.

If a certain time elapses to clean semiconductor wafers on the top ringand the rotary transporter, it directly affects the processing time forsemiconductor wafers. However, the cleaning of semiconductor wafers inthe reversing device during the waiting time does not affect theprocessing time of the polishing apparatus. Accordingly, it ispreferable to apply cleaning water on the top ring and the rotarytransporter intensively in a short time, and to clean semiconductorwafers in the reversing device with pure water at a rate enough toprevent the semiconductor wafers from being dried, e.g., to cleansemiconductor wafers in the reversing device intermittently with purewater.

According to the present invention, the polishing apparatus can changetransfer routes to comply with the required cleaning processes formaintaining a desired number of cleaning stages depending on variouspolishing processes without reducing the processing capability per unitinstallation area, and also to shorten the processing time of each ofthe cleaning processes by assigning the cleaning process which needs along period of time to at least two cleaning apparatuses, for therebyincreasing the number of processed workpieces per unit time, i.e.,throughput.

Furthermore, it is possible to shorten the time required to transfer aworkpiece to be polished, such as a semiconductor wafer, to the topring, for thereby greatly increasing the number of processed workpiecesper unit time, i.e., throughput.

Moreover, in as much as polished workpieces can wait while beingprocessed in cleaning processes, a plurality of cleaning processeshaving different processing times can be performed parallel to eachother on a plurality of polished workpieces. Specifically, the transferroutes will not be blocked by the cleaning processes which need a longperiod of time, and polished workpieces can be supplied uninterruptedlyto the cleaning processes.

In addition, since chambers in which cleanliness of atmosphere isdifferent from one another are separated by partitions, the atmospherein a contaminated chamber is prevented from flowing into a clean chamberand hence from lowering the cleanliness in the clean chamber.

FIG. 49 shows a layout of various components of a polishing apparatusaccording to a second embodiment of the present invention. As shown inFIG. 49, a polishing apparatus according to the present inventioncomprises two rotatable load-unload stages 501 each for placing a wafercassette 540 which houses a number of semiconductor wafers. A transferrobot 502 having two hands is disposed at a position where the transferrobot 502 can access the respective wafer cassettes 540 on therespective load-unload stages 501.

The transfer robot 502 has two hands which are located in a verticallyspaced relationship, and the upper hand is used only for handling aclean and dry semiconductor wafer and the lower hand is used only forhandling a dirty and wet semiconductor wafer. Two cleaning apparatuses503 are disposed on both sides of the transfer robot 502 for cleaningand drying the semiconductor wafer which has been polished. The cleaningapparatuses 503 are disposed at positions that can be accessed by thehands of the transfer robot 502. Two reversing devices 504 and 505 forreversing semiconductor wafers are disposed at positions which aresymmetric about a center 502 c of the transfer robot 502 with respect tothe load-unload stages 501 and can be accessed by the hands of thetransfer robot 502.

The reversing device 504 has a chuck mechanism for chucking asemiconductor wafer and a reversing mechanism for reversing thesemiconductor wafer, and handles only a clean and dry semiconductorwafer. The reversing device 505 has a rinsing mechanism for cleaning asemiconductor wafer, in addition to the chuck mechanism and thereversing mechanism, and handles only a dirty and wet semiconductorwafer. A transfer robot 506 having two hands is disposed in such amanner that the transfer robot 506 and the transfer robot 502 aresymmetric with respect to a line L, interconnecting a center 504 c ofthe semiconductor wafer chucked by the reversing device 504 and a center505 c of the semiconductor wafer chucked by the reversing device 505.The transfer robot 506 is disposed at a position where the hands of thetransfer robot 506 can access the reversing devices 504 and 505 andstages of a rotary transporter 519. The two hands of the transfer robot506 are located in a vertically spaced relationship, and the upper handis used only for handling a clean and dry semiconductor wafer and thelower hand is used only for handling a dirty and wet semiconductorwafer.

Two cleaning apparatuses 507 for cleaning a semiconductor wafer whichhas been polished are disposed on both sides of the transfer robot 506.Each of the cleaning apparatuses 507 performs a cleaning processdifferent from the cleaning process in each of the cleaning apparatuses503. The cleaning apparatuses 507 are disposed at positions that can beaccessed by the hands of the transfer robot 506. Two transfer robots 508having a single hand are disposed at the opposite sides of the reversingdevices 504, 505 with respect to the respective cleaning apparatuses507. The transfer robots 508 are disposed at positions where the handsof the transfer robots 508 can access the cleaning apparatuses 507 and astage of the rotary transporter 519.

The polishing apparatus has a housing 530 for enclosing variousapparatuses and components therein. The housing 530 constitutes anenclosing structure. The interior of the housing 530 is partitioned intoa plurality of compartments or chambers (including a polishing chamberand a cleaning chamber). The cleaning chamber 530A extends from an areawhere the two transfer robots 508 are located to an area where theload-unload stages 501 are located. A partition wall 531 is providedadjacent to the transfer robots 508 in the cleaning chamber 530A, and apolishing chamber 530B is located at the opposite side of the cleaningchamber 530A with respect to the partition wall 531. In the polishingchamber 530B, two turntables 509 and 510, and two top rings 512 areprovided, and one of the top rings 512 holds a semiconductor wafer andpresses the semiconductor wafer against the turntable 509 and the otherof the top ring 512 holds a semiconductor wafer and presses thesemiconductor wafer against the turntable 510.

FIG. 50 shows the relationship between the top ring 512 and theturntable 509 or 510. As shown in FIG. 50, the top ring 512 is supportedby a rotatable shaft 532 which is suspended from a top ring arm 511. Thetop ring arm 511 is supported by a rotating shaft 533 which is angularlypositionable, and hence the top ring 512 can access the turntable 509 or510. Each of the top rings 512 can press the semiconductor wafer againstthe turntable 509 or 510 under a desired pressure by an air cylinderprovided in the top ring arm 511. A polishing liquid supply nozzle 513is provided respectively for supplying a polishing liquid to a centralportion of the turntable 509 or 510. A dresser 514 for dressing theturntable 509 or 510 is provided respectively adjacent to the turntable509 or 510. A polishing pad (polishing cloth) or an abrading plate(fixed-abrasives) is attached to the upper surface of the turntable 509or 510.

Next, a pusher unit as a transferring device for transferringsemiconductor wafers between the transfer robots 506 and 508, and thetop ring 512 will be described. The pusher unit is disposed in a centralportion of a space surrounded by the two turntables 509, 510 and thethree transfer robots 506 and 508. The pusher unit is of three typesincluding two rotary transporter types and one linearly movable tabletype. Next, three types of the pusher unit will be described below.

1) Rotary Transporter Type A

FIGS. 51 and 52 show a detailed structure of the rotary transporter typeA, and FIG. 51 is a plan view of the rotary transporter type A and FIG.52 is an elevational view of the rotary transporter type A. As shown inFIGS. 51 and 52, two pushers 517 are provided along swing loci of thetop rings 512, respectively. Each of the pushers 517 constitutes adedicated wafer transfer mechanism for transferring a semiconductorwafer to or from the top ring 512. Each of the pusher 517 has anelevating mechanism so that the pusher 517 can move vertically between awafer transfer position for transferring the semiconductor wafer to thetop ring 512 and a supply position for supplying the semiconductor waferto the pusher 517. Between the pushers 517 and the cleaning chamber530A, there is provided a rotary transporter 519 which constitutes atransfer mechanism for transferring the semiconductor wafers between thepusher 517, and the transfer robot 506 and the transfer robots 508 (seeFIGS. 49, 51 and 52).

The rotary transporter 519 is rotatable horizontally through 360°, andcomprises an indexing mechanism and four stages 515, 516 for placingsemiconductor wafers. The two stages 515 and the two stages 516 arepositioned along a circle having a certain radius from a rotation centerof the rotary transporter 519 at equally angular intervals. The twostages 515 serve as a load stage for placing the semiconductor wafer tobe polished and the two stages 516 serve as an unload stage for placingthe semiconductor wafer which has been polished. The stages 515 and 516are not necessarily assigned to the load stage and the unload stage,respectively.

As shown in FIG. 49, the rotation center of the rotary transporter 519is disposed at a position where the transfer robot 506, the transferrobots 508 and the top rings 512 can access the respective stages 515and 516. In this embodiment, the rotary transporter 519, the turntables509, 510 and the top rings 512 are arranged such that the distancesbetween the rotating shaft of the rotary transporter 519 and therotating shafts of the turntables 509, 510 are equal and the distancesbetween the rotating shaft of the rotary transporter 519 and therotating shafts 533 of the top rings 512 are equal. A cover 521 isprovided so that the rotary transporter 519 is located in the polishingchamber 530B. The cover 521 has an opening for allowing thesemiconductor wafers to pass therethrough so that the semiconductorwafers are transferred to or from the rotary transporter 519, and ashutter 518 is provided at the opening. Cleaning nozzles 543 forsupplying cleaning liquid to wafers to clean the wafers are providedalong wafer transfer routes to or from the robots in the cover 521.Cleaning nozzles 542 for supplying cleaning liquid to the top rings 512after polishing to clean them are provided on or adjacent to the pushers517. The cleaning nozzles 542 for cleaning the top rings 512 may be usedfor preventing the top rings 512 from being dried while the top rings donot perform a polishing process.

2) Rotary Transporter Type B

FIGS. 53 and 54 show a detailed structure of the rotary transporter typeB, and FIG. 53 is a plan view of the rotary transporter type B and FIG.54 is an elevational view of the rotary transporter type B. As shown inFIG. 49, between the top rings 512 and the cleaning chamber 530A, thereis provided a rotary transporter 519 which constitutes a transfermechanism for transferring the semiconductor wafers between the toprings 512, and the transfer robot 506 and the transfer robots 508. Therotary transporter 519 is rotatable horizontally through 360°, and hasan indexing mechanism. The rotary transporter 519 has four pushers 515,516 constituting a wafer transfer mechanism for transferring thesemiconductor wafers to or from the top rings 512. The four pushers 515,516 are mounted on the rotary transporter 519 so as to be rotatabletogether with the rotary transporter 519. The two pushers 515 and thetwo pushers 516 are positioned along a circle having a certain radiusfrom a rotation center of the rotary transporter 519 at equally angularintervals. The two pushers 515 serve as a load pusher for placing thesemiconductor wafer to be polished and the two pushers 516 serve as anunload pusher for placing the semiconductor wafer which has beenpolished. The pushers 515 and 516 are not necessarily assigned to theload pusher and the unload pusher, respectively.

The pushers 515, 516 have an elevating mechanism so that the pushers515, 516 can move vertically between a wafer transfer position fortransferring the semiconductor wafers to the top rings 512 and a supplyposition for supplying the semiconductor wafers to the pushers 515, 516.As shown in FIG. 49, the rotation center of the rotary transporter 519is disposed at a position where the transfer robot 506, the transferrobots 508 and the top rings 512 can access the respective pushers 515and 516. The cover 521, the shutter 518, the cleaning nozzles forcleaning the semiconductor wafers, and the cleaning nozzles for cleaningthe top rings have the same structures as those in type A, and hencedescription thereof will not be made.

3) Linearly Movable Table Type

FIGS. 55 and 56 show a detailed structure of the linearly movable tabletype, and FIG. 55 is a plan view of the linearly movable table type andFIG. 56 is an elevational view of the linearly movable table type. Asshown in FIGS. 55 and 56, two pushers 517 are provided along swing lociof the top rings 512, respectively. Each of the pushers 517 constitutesa dedicated wafer transfer mechanism for transferring a semiconductorwafer to or from the top ring 512. Each of the pusher 517 has anelevating mechanism so that the pusher 517 can move vertically between awafer transfer position for transferring the semiconductor wafer to thetop ring 512 and a supply position for supplying the semiconductor waferto the pusher 517. Between the pushers 517 and the cleaning chamber530A, there are provided two transfer mechanism 525 for transferring thesemiconductor wafers between the pushers 517, and the transfer robot 506and the transfer robots 508. One of the transfer mechanisms 525 isprovided for the turntable 509 and the other of the transfer mechanisms525 is provided for the turntable 510. The two transfer mechanisms 525have a stage 515 and a stage 516, respectively. The stages 515 and 516are located above the pushers 517, respectively, and movable linearlyand individually in respective horizontal planes. The stage 515 is aload stage for transferring the semiconductor wafer to the top ring, andthe stage 516 is an unload stage for receiving the semiconductor waferfrom the top ring 512. The two transfer mechanisms 525 are linearlymovable between the transfer position to and from the top ring 512 andthe transfer position for the transfer robot 508 located in line withthe pusher 517 and the centrally located transfer robot 506. Thetransfer mechanisms 525 have two straight rails 526, respectively whichare positioned at different heights. Each of the rails 526 supports thestage 515 or 516 which is slidable along the rail 526. The two stages515 and 516 in each of the transfer mechanisms 525 are positioned sothat they do not interfere with each other vertically, and movableindividually in a horizontal direction. The stages 515 and 516 aremovable along the rails 526, respectively by a ball screw mechanism anda motor (not shown). By this arrangement, when the two stages 515 and516 move, the positions of the two stages 515 and 516 can be replaced inplan. The moving mechanism of the transfer mechanism 525 includes apositional mechanism. When the stages 515 and 516 on which thesemiconductor wafers are placed move to wafer transfer positions to thetop rings 512, the pushers 517 located below the respective top rings512 push the semiconductor wafers upwardly to transfer the semiconductorwafers to the respective top rings 512. Conversely, when the stages 515,516 on which the semiconductor wafers are not placed move to the samepositions, the pushers 517 receive the semiconductor wafers from therespective top rings, and move downwardly for thereby placing thesemiconductor wafers on the respective stages 515 and 516.

The transfer mechanisms 525 are located in the polishing chamber 530B.The partition wall for defining the polishing chamber 530B has anopening for transferring the semiconductor wafers to or from thetransfer mechanisms 525, and a shutter 518 is provided at the opening.Cleaning nozzles for supplying cleaning liquid to wafers to clean themare provided along wafer transfer routes to or from the robots in thechamber 530B. Cleaning nozzles for supplying cleaning liquid to the toprings 512 after polishing to clean them are provided on or adjacent tothe pushers 517. The cleaning nozzles for cleaning the top rings 512 maybe used for preventing the top rings 512 from being dried while the toprings do not perform a polishing process.

Next, the operation of the polishing apparatus having the abovestructure will be described below. Semiconductor wafers to be polishedare housed in the wafer cassette 540, and the wafer cassette 540 isplaced on the load-unload stage 501. After the whole processingconditions in the polishing apparatus are inputted, the polishingapparatus starts automatic operation. In this polishing apparatus, somepolishing processes can be performed, and in the following description,in the case where the number of semiconductor wafers counted from theuppermost position of the wafer cassette is odd, such odd numbers of thesemiconductor wafers are polished on the turntable 509 one afteranother. Further, in the case where the number of semiconductor waferscounted from the uppermost position of the wafer cassette is even, sucheven numbers of the semiconductor wafers are polished on the turntable510 one after another. Next, the polishing processes will be describedbelow.

In this case, with regard to the pusher unit, the rotary transportertype A is basically described, and the rotary transporter type B isdescribed in parenthesis. Further, with regard to the pusher unit of thelinearly movable table type, the rotary motion of the rotary transporter519 is replaced with the linear motion of the table, and other motionsare the same as the rotary transporter types A and B.

1. The load-unload stage 501 is angularly positionally adjusted, and thewafer cassette 540 turns its front face to the direction in which thetransfer robot 502 can transfer the semiconductor wafers to or from thewafer cassette 540.

2. The transfer robot 502 adjusts its angular position and heightposition, and the hand of the transfer robot 502 holds the semiconductorwafer in the wafer cassette 540 under vacuum, and takes out thesemiconductor wafer from the wafer cassette 540. In this case, in thetransfer robot 502, the hand for handling a clean semiconductor wafer isused.

3. The transfer robot 502 adjusts again its angular position and heightposition while the transfer robot 502 holds the semiconductor wafer, andtransfers the semiconductor wafer to the reversing device 504.

4. The reversing device 504 chucks the semiconductor wafer transferredfrom the transfer robot 502, and after it is confirmed that thesemiconductor wafer is normally chucked, the semiconductor wafer isrotated through 180° to make the surface thereof to be polished facingdownward.

5. After it is confirmed that the reversing device 504 is normallyrotated through 180°, the transfer robot 506 adjusts its angularposition and height position. Thereafter, the chuck of the reversingdevice 504 is opened and the hand of the transfer robot 506 receives thesemiconductor wafer from the reversing device 504. In this case, in thetransfer robot 506, the hand for handling a clean semiconductor wafer isused.

6. The transfer robot 506 adjusts again its angular position and heightposition, and after it is confirmed that the semiconductor wafer is notplaced on the stage 515 (pusher 515) of the rotary transporter 519, theshutter 518 is opened and the semiconductor wafer is transferred to thestage 515 (pusher 515).

7. After it is confirmed that the semiconductor wafer is transferred tothe stage 515 (pusher 515), the shutter 518 is closed and the rotarytransporter 519 is rotated through 90° or 270° to allow the stage 515(pusher 515) to move to a wafer transfer position to the top ring 512.

8. After it is confirmed that the stage 515 (pusher 515) moves to aposition where the top ring 512 can access the stage 515, the pusher 517is elevated to receive the semiconductor wafer from the stage 515, andfurther elevated to chuck the top ring 512 (the pusher 515 is elevatedto chuck the top ring 512). Thereafter, the stage of the pusher 517 onwhich the semiconductor wafer is placed is further elevated, thebackside surface of the semiconductor wafer contacts the wafer holdingsurface of the top ring 512, and at the same time, the top ring 512holds the semiconductor wafer under vacuum.

9. After it is confirmed that the top ring 512 holds the semiconductorwafer normally under vacuum, the pusher 517 is lowered. After it isconfirmed that lowering of the pusher 517 is completed, the rotarytransporter 519 is rotated in the direction opposite to the aboverotating direction through 90° or 270°. At this time, the unload stage516 (pusher 516) is located at a wafer transfer position from the topring 512. Further, at the same time that the rotary transporter 519 isrotated, the rotating shaft 533 for supporting the top ring arm 511 isrotated, and top ring 512 moves to a polishing position on the turntable509.

10. After it is confirmed that the top ring 512 moves to the polishingposition, the turntable 509 and the top ring 512 are rotated in the samedirection at predetermined speeds, and a polishing liquid is suppliedonto the turntable 509 from the polishing liquid supply nozzle 513 in apredetermined kind and amount. Thereafter, the top ring 512 is lowered,and after it is confirmed that the top ring 512 reaches the turntable509, the semiconductor wafer is pressed against the turntable 509 by thetop ring 512 under a predetermined pressure and the semiconductor waferis polished for a predetermined time. The above predetermined speed,kind, amount, pressure, time, and the like are inputted in advance.While the semiconductor wafer is polished, a subsequent semiconductorwafer to be polished is transferred in the same manner described above,and the subsequent semiconductor wafer is transferred to the load stage515 (pusher 515).

11. After polishing of the semiconductor wafer is completed, the supplyof the polishing liquid from the polishing liquid supply nozzle 513 isstopped, and the top ring 512 holds the semiconductor wafer undervacuum. After it is confirmed that the semiconductor wafer is held bythe top ring 512 under vacuum, the shaft 533 for supporting the top ringarm 511 is rotated so that the top ring 512 moves to a position wherethe top ring 512 projects from the outer periphery of the turntable 509by about half.

12. After it is confirmed that the top ring 512 projects from the outerperiphery of the turntable 509 by about half, the shaft 533 forsupporting the top ring arm 511 is rotated, and at the same time, thetop ring 512 moves to a wafer transfer position of the top ring 512located above the pusher 517 while the top ring 512 is being elevated.At this time, the unload stage 516 (pusher 516) is located at the wafertransfer position from the top ring 512 because the rotary transporter519 remains in the state of the above step 9.

13. After it is confirmed that the top ring 512 is positioned above thepusher 517 (pusher 516), the pusher 517 (pusher 516) is elevated toallow the pusher 517 (pusher 516) to chuck the top ring 512, and at thesame time, the vacuum is shut off. Then, air or nitrogen and pure waterare blown from the lower surface of the top ring 512, and thesemiconductor wafer is removed from the top ring 512 and placed on thepusher 517 (pusher 516).

14. After the semiconductor wafer is removed from the top ring 512, thepusher 517 is lowered to a position below the stage (the pusher 516 islowered to a position where the transfer robot 508 can transfer thesemiconductor wafer).

15. The pusher 517 (pusher 516) is lowered, and after it is confirmedthat the semiconductor wafer is placed on the stage 516 (pusher 516),the rotary transporter 519 is rotated through 90° or 270°. Thus, asubsequent semiconductor wafer, to be polished, which has beentransferred to the stage 515 (pusher 515) moves to a wafer transferposition to the top ring 512, and is transferred in the same manner asdescribed above and polished. At the same time, pure water (deionizedwater) is ejected from the rinsing nozzles to clean the top ring 512,and the pure water (deionized water) is supplied to the wafer placed onthe stage 516 for preventing the wafer from drying. Between the finishof the preceding wafer-polishing and the start of the subsequentwafer-polishing, the dressing is conducted by the dresser 514 to recoverthe optimum polishing surface of the turntable 509 or 510.

16. After the subsequent semiconductor wafer is transferred to the topring 512, the rotary transporter 519 is rotated, and after it isconfirmed that the stage 516 (pusher 516) moves to a position that canbe accessed by the transfer robot 508, the shutter 518 is opened and thetransfer robot 508 adjusts its angular position and height position toreceive the semiconductor wafer from the stage 516 (pusher 516).

17. After the transfer robot 508 receives the semiconductor wafer fromthe stage 516 (pusher 516), the shutter 518 is closed and the transferrobot 508 adjusts its angular position and height position to transferthe semiconductor wafer to the cleaning apparatus 507, and at the sametime, the cleaning apparatus 507 chucks the semiconductor wafer.

18. After it is confirmed that the cleaning apparatus 507 chucks thesemiconductor wafer normally, a primary cleaning of the polishedsemiconductor wafer is conducted.

19. After the cleaning process of the cleaning apparatus 507 isconducted, the transfer robot 506 moves to a position where the transferrobot 506 can access the cleaning apparatus 507, and at the same time,the transfer robot 506 adjusts its angular position and height positionand receives the semiconductor wafer by the hand. In this case, in thetransfer robot 506, the hand for handling a dirty semiconductor wafer isused.

20. The transfer robot 506 adjusts again its angular position and heightposition and transfers the semiconductor wafer to the reversing device505, and at the same time, the reversing device 505 chucks thesemiconductor wafer.

21. After it is confirmed that the reversing device 505 chucks thesemiconductor wafer normally, pure water is ejected from the rinsingnozzles attached to the reversing device 505 to prevent thesemiconductor wafer from being dried. At the same time, the reversingdevice 505 is rotated through 180° to make the polished surface of thesemiconductor wafer facing upward.

22. After it is confirmed that the reversing device 505 is rotatednormally through 180°, the transfer robot 502 adjusts its angularposition and height position to receive the semiconductor wafer from thereversing device 505 by the hand, and at the same time, the reversingdevice 505 opens the chuck mechanism. In this case, in the transferrobot 502, the hand for handling a dirty semiconductor wafer is used.

23. The transfer robot 502 adjusts its angular position and heightposition, and transfers the semiconductor wafer to the cleaningapparatus 503, and at the same time, the cleaning apparatus 503 chucksthe semiconductor wafer.

24. After it is confirmed that the cleaning apparatus 503 chucks thesemiconductor wafer normally, a secondary cleaning of the polishedsemiconductor wafer is conducted.

25. After cleaning of the semiconductor wafer by the cleaning apparatus503 is completed, the transfer robot 502 adjusts its angular positionand height position to receive the semiconductor wafer from the cleaningapparatus 503 by the hand. In this case, in the transfer robot 502, thehand for handling a clean semiconductor wafer is used.

26. The transfer robot 502 adjusts again its angular position and heightposition, and transfers the semiconductor wafer to the wafer cassette540 in which the polished semiconductor wafer is returned to itsoriginal position stored before polishing.

27. Even numbers of the semiconductor wafers counted from the uppermostposition of the wafer cassette after the second semiconductor wafer aretransferred to the turntable 510, polished, cleaned and returned to thewafer cassette one after another in the same manner as described above.

Next, the operation of the pusher unit of the rotary transporter type Awill be described below with reference to FIGS. 57 and 58. FIG. 57 is aplan view showing the relationship of the top ring, the rotarytransporter, the pushers and the transfer robots, and FIGS. 58A through58D are views showing the manner in which the pusher is operated.

As shown in FIG. 57, the semiconductor wafer 602 to be transferred tothe top ring 512 is transferred to the rotary transporter 519 from thedirection shown by an arrow 710 by the transfer robot 506. Thesemiconductor wafer is placed on shoulders of pins 601 fixed to therotary transporter 519 by the robot hand 660. At this time, the waferholding portion of the robot hand 660 and the pins 601 contact thesemiconductor wafer 602 at different positions of the outer periphery ofthe semiconductor wafer 602. Thereafter, the rotary transporter 519 isrotated by a motor 700 (see FIG. 52), and the semiconductor wafer 602 ismoved to a transfer position 715 to the top ring 512 and positionedabove the pusher 517.

FIG. 58A shows the state in which the semiconductor wafer 602 is placedon the rotary transporter 519 and transferred to a position above thepusher 517. In FIG. 58A, the top ring 512 is positioned above the rotarytransporter 519, and the pusher 517 is positioned below the rotarytransporter 519.

Next, the pusher 517 is elevated by an air cylinder 605 to push thesemiconductor wafer 602 placed on the shoulders of the pins 601upwardly, and the semiconductor wafer 602 is transferred to the stage606 of the pusher 517. At this time, the stage 606 contacts thesemiconductor wafer 602 at a position different from positions where thepins 601 contact the semiconductor wafer 602, but the contacting portionbetween the stage 606 and the semiconductor wafer 602 is common partlyto a position where the robot hand 660 contacts the semiconductor wafer602. FIG. 58B shows the state in which the air cylinder 605 of thepusher 517 is operated, and the semiconductor wafer 602 on the rotarytransporter 519 contacts the stage 606 of the pusher 517. At this time,a centering guide 607 and a centering guide 608 of the pusher 517contact with each other, and hence the stage 606 and the stage 609 arelocated at a fixed position.

FIG. 58C shows the state in which the air cylinder 605 is furtheroperated to push the semiconductor wafer 602 from the rotary transporter519 upwardly, and the stage 609 contacts the top ring 512. When thestage 606 receives the semiconductor wafer 602 from the rotarytransporter 519, the centering guide 607 and the centering guide 608 arebrought out of contact with each other, and hence the stage 606 canfreely move horizontally. This centering action can be carried out byincorporating linear guides which are perpendicularly provided to eachother in section A (see FIG. 58A).

A guide 610 of the stage 609 has a tapered surface, and when the topring 512 contacts the guide 610, the pusher 517 is guided so that topring 512 is positioned in the guide 610. That is, the pusher 517 has afunction for adjusting the position of the pusher 517 with respect tothe top ring 512. In order to cushion impact caused by contact betweenthe stage 609 and the top ring 512, the springs 611 and 612 areincorporated, and a shock absorber 613 is incorporated to adjust acontact position between the stage 609 and the top ring 512.

FIG. 58D shows the state in which the air cylinder 614 is furtheroperated from the state shown in FIG. 58C to elevate the stage 606 onwhich the semiconductor wafer 602 is placed, and the semiconductor wafer602 contacts the holding surface of the top ring 512. Even in thisstate, the springs 611 and 612 have such a function that the stage 606does not press the semiconductor wafer 602 against the top ring 512under a pressure more than necessary.

By a series of operations described above, the semiconductor wafer 602on the rotary transporter 519 is transferred to the top ring 512.

In the case where the semiconductor wafer 602 is transferred from thetop ring 512 to the rotary transporter 519, the pusher 517 is operatedin the state shown in FIG. 58C, and the semiconductor wafer 602 isremoved form the top ring 512 in this state. After the semiconductorwafer 602 is removed from the top ring 512, the pusher 517 is operatedin the order of FIG. 58C, FIG. 58B and FIG. 58A in a series ofoperations which are reverse to a series of operations in which thesemiconductor wafer is held by the top ring under vacuum. In thismanner, the semiconductor wafer 602 held by the top ring 512 undervacuum is transferred to the rotary transporter 519. At this time, thesemiconductor wafer 602 is placed on the pins 601 of the rotarytransporter 519. Thereafter, the rotary transporter 519 is rotated bythe motor 700 to a wafer removing position, and then the semiconductorwafer 602 is transferred in the direction shown by an arrow 711 by therobot hand 680 of the transfer robot 508.

FIG. 59 is a plan view showing a modified embodiment of the polishingapparatus according to the present invention.

In this embodiment, two load pushers 515 are disposed along a diagonalline of the rotary transporter 519, and two unload pushers 516 aredisposed along another diagonal line of the rotary transporter 519. Thetotal of four pushers 515 and 516 are provided on the rotary transporter519.

FIGS. 60 through 64 are diagrams illustrative of a process of polishinga semiconductor wafer with the polishing apparatus shown in FIGS. 49 and59. To be more specific, FIGS. 60 through 64 show a process in which asemiconductor wafer is taken out from a wafer cassette CS1, polished,cleaned, and returned to the wafer cassette CS1, and a process in whicha semiconductor wafer is taken out from another wafer cassette CS2,polished, cleaned, and returned to the wafer cassette CS2. In FIGS. 60through 64, the wafer cassettes 540 are represented by CS1 and CS2, thetransfer robots 502, 506 and 508 are represented by RB1, RB2, RB3 andRB4, the cleaning apparatuses 503 and 507 are represented by CL1-1,CL1-2, CL2-1 and CL2-2, and the reversing devices 504 and 505 arerepresented by T. ov1 and T. ov2, the turntables 509 and 510 arerepresented by TT1 and TT2, the top rings 512 are represented by TR1 andTR2, the load stages (or pushers) of the rotary transporter 519 arerepresented by In-1L and In-2L, and the unload stages (or pushers) ofthe rotary transporter 519 are represented by In-1UL and In-2UL.

As shown in FIGS. 60 through 64, one semiconductor wafer is processed inthe following route: the wafer cassette (CS1)→the transfer robot(RB1)→the reversing device (T. ov1)→the transfer robot (RB2)→the loadstage (or pusher)(In-1L)→the top ring (TR1)→the turntable (TT1)→theunload stage (or pusher) (In-1UL)→the transfer robot (RB3)→the cleaningapparatuse (CL1-1)→the transfer robot (RB2)→the reversing device (T.ov2)→the transfer robot (RB1)→the cleaning apparatus (CL2-1)→thetransfer robot (RB1)→the wafer cassette (CS1).

The other semiconductor wafer is processed in the following route: thewafer cassette (CS2)→the transfer robot (RB1)→the reversing device (T.ov1)→the transfer robot (RB2)→the load stage (or pusher)(In-2L)→the topring (TR2)→the turntable (TT2)→the unload stage (or pusher) (In-2UL)→thetransfer robot (RB4)→the cleaning apparatuses (CL1-2)→the transfer robot(RB2)→the reversing device (T. ov2)→the transfer robot (RB1)→thecleaning apparatus (CL2-2)→the transfer robot (RB1)→the wafer cassette(CS2).

As shown in FIGS. 60 through 64, among the four stages of the rotarytransporter 519, the two stages transfer the semiconductor wafer to besupplied to the turntable 509, the remaining two stages transfer thesemiconductor wafer to be supplied to the turntable 510. The wafer whichis polished by the turntable 509 and the wafer which is polished by theturntable 510 are commonly handled by the rotary transporter 519 and therobot 506, the robot 502, and the reversing devices 504, 505.

FIG. 65 shows a layout of various components of a polishing apparatusaccording to a third embodiment of the present invention. As shown inFIG. 65, a polishing apparatus according to the present inventioncomprises two rotatable load-unload stages 501 each for placing a wafercassette 540 which houses a number of semiconductor wafers. A transferrobot 502 having two hands is disposed at a position where the transferrobot 502 can access the respective wafer cassettes 540 on therespective load-unload stages 501.

The transfer robot 502 has two hands, one of which is used only forhandling a clean semiconductor wafer and the other of which is used onlyfor handling a dirty semiconductor wafer. Two cleaning apparatuses 503are disposed on both sides of the transfer robot 502 for cleaning anddrying the semiconductor wafer which has been polished. The cleaningapparatuses 503 are disposed at positions that can be accessed by thehands of the transfer robot 502. Two reversing devices 504 and 505 forreversing semiconductor wafers are disposed at positions which aresymmetric about a center 502 c of the transfer robot 502 with respect tothe load-unload stages 501 and can be accessed by the hands of thetransfer robot 502.

The reversing device 504 has a chuck mechanism for chucking asemiconductor wafer and a reversing mechanism for reversing thesemiconductor wafer, and handles only a clean semiconductor wafer. Thereversing device 505 has a rinsing mechanism for cleaning asemiconductor wafer, in addition to the chuck mechanism and thereversing mechanism, and handles only a dirty semiconductor wafer. Atransfer robot 506 having two hands is disposed in such a manner thatthe transfer robot 506 and the transfer robot 502 are symmetric withrespect to a line L₁ interconnecting a center 504 c of the semiconductorwafer chucked by the reversing device 504 and a center 505 c of thesemiconductor wafer chucked by the reversing device 505. The transferrobot 506 is disposed at a position where the hands of the transferrobot 506 can access the reversing devices 504 and 505. The transferrobot 506 has the two hands, one of which is used only for handling aclean semiconductor wafer and the other of which is used only forhandling a dirty semiconductor wafer.

Two cleaning apparatuses 507 for cleaning a semiconductor wafer whichhas been polished are disposed on both sides of the transfer robot 506.Each of the cleaning apparatuses 507 performs a cleaning processdifferent from the cleaning process in each of the cleaning apparatuses503. The cleaning apparatuses 507 are disposed at positions that can beaccessed by the hands of the transfer robot 506. Two transfer robots 508having a single hand are disposed at the opposite sides of the reversingdevices 504, 505 with respect to the respective cleaning apparatuses507. The transfer robots 508 are disposed at positions where the handsof the transfer robots 508 can access the cleaning apparatuses 507,respectively. Between the two transfer robots 508, there is provided awafer station 520 having a rinsing mechanism. In order to preventrinsing water from being scattered around, a cover is provided toenclose the wafer station 520, and has three shutters on three sidesurfaces.

The polishing apparatus has a housing 530 for enclosing variousapparatuses and components therein. The housing 530 constitutes anenclosing structure. The interior of the housing 530 is partitioned intoa plurality of compartments or chambers (including a polishing chamberand a cleaning chamber). The cleaning chamber 530A extends from an areawhere the two transfer robots 508 are located to an area where theload-unload stages 501 are located. A partition wall 531 is providedadjacent to the transfer robots 508 in the cleaning chamber 530A, and apolishing chamber 530B is located at the opposite side of the cleaningchamber 530A with respect to the partition wall 531. In the polishingchamber 530B, two turntables 509 and 510, and two top rings 512 areprovided, and one of the top rings 512 holds a semiconductor wafer andpresses the semiconductor wafer against the turntable 509 and the otherof the top ring 512 holds a semiconductor wafer and presses thesemiconductor wafer against the turntable 510.

In the polishing chamber 530B, two rotary transporters 519 are providedso as to correspond to the two top rings 512, respectively. Each of therotary transporter 519 has a load pusher 515 for transferring asemiconductor wafer to the top ring 512 and an unload pusher 516 fortransferring a semiconductor wafer from the top ring 512 thereto. Theload pusher 515 and the unload pusher 516 are positioned along a circlehaving a certain radius from a rotation center of the rotary transporter519 at equally angular intervals. A set of the load pusher 515 and theunload pusher 516 are provided on the rotary transporter 519. That is,the load pusher 515 and the unload pusher 516 are prepared for each ofthe turntables 509 and 510. By rotating the index table 519 forsupporting the respective pushers, the load pusher 515 and the unloadpusher 516 can move to a first position where they can transfer thesemiconductor wafer to or from the transfer robot 508, and a secondposition where they can transfer the semiconductor wafer to or from thetop ring 512. The load pusher 515 moves to substantially the sameposition as the unload pusher 516, and at the same time, the unloadpusher 516 moves to substantially the same position as the load pusher515. Thus, the top ring 512 and the transfer robot 508 can accesssimultaneously the load pusher and the unload pusher. Further, the tworotary transporters 519 can be controlled independently from each other.

Further, the load pusher 515 and the unload pusher 516 have an elevatingmechanism so that they can access the top ring 512 and the transferrobot 508. The load pusher 515 has an automatic centering mechanismwhich is operated only when the load pusher 515 is elevated to reach thetop ring 512 for thereby transferring the semiconductor wafer. The loadpusher 515 is movable within such an area that an installation error ofthe top ring 512 can be absorbed, and hence the load pusher 515 cantransfer the semiconductor wafer to the top ring 512. Further, when thetransfer robot 508 transfer the semiconductor wafer to the load pusher515, the load pusher 515 is located at a lowermost position and is fixedto be stationary.

The unload pusher 516 has an automatic centering mechanism which isoperated only when the unload pusher 516 is elevated to reach the topring 512 for thereby receiving the semiconductor wafer. The unloadpusher 516 is movable within such an area that an installation error ofthe top ring 512 can be absorbed, and hence the unload pusher 516 canreceive the semiconductor wafer from the top ring 512. Further, when thetransfer robot 508 receives the semiconductor wafer from the unloadpusher 516, the unload pusher 516 is located at a lowermost position andis fixed to be stationary. The pushers 515 and 516 have substantiallythe same structure and are operated in the same manner as that shown inFIGS. 58A through 58D.

Rinsing nozzles for supplying cleaning liquid to wafers are provided atthe first position to clean the wafers transferred from the top ring512. Cleaning nozzles for supplying cleaning liquid to the top rings 512are provided at the second position for cleaning the top ring 512 whichreleases the semiconductor wafer. Sensors are provided at the first andsecond positions for detecting whether the semiconductor wafer exists ornot. The partition wall has openings to allow the semiconductor wafer topass therethrough at a position between the load pusher 515 and thetransfer robot 508 and a position between the unload pusher 516 and thetransfer robot 508, and shutters 518 are provided at the openings.

FIG. 66 shows the relationship between the top ring 512 and theturntable 509 or 510. As shown in FIG. 66, the top ring 512 is supportedby a rotatable shaft 532 which is suspended from a top ring arm 511. Thetop ring arm 511 is supported by a rotating shaft 533 which is angularlypositionable, and hence the top ring 512 can access the turntable 509 or510. Each of the top rings 512 can press the semiconductor wafer againstthe turntable 509 or 510 under a desired pressure by an air cylinderprovided in the top ring arm 511. A polishing liquid supply nozzle 513is provided for supplying a polishing liquid to a central portion of theturntables 509 or 510. A dresser 514 for dressing each of the turntables509 and 510 is provided adjacent to the turntable 509 or 510. Apolishing cloth or an abrading plate (a fixed-abrasive plate) isattached to the upper surface of the turntable 509 or 510. The rotarytransporter 519 having the load pusher 515 and the unload pusher 516 isprovided adjacent to the rotating shaft 533 of the top ring 512.

Next, the operation of the polishing apparatus having the abovestructure will be described below. Semiconductor wafers to be polishedare housed in the wafer cassette 540, and the wafer cassette 540 isplaced on the load-unload stage 501. After the whole processingconditions in the polishing apparatus are inputted, the polishingapparatus starts automatic operation. In this polishing apparatus, somepolishing processes can be performed, and in the following description,in the case where the number of semiconductor wafers counted from theuppermost position of the wafer cassette is odd, such odd numbers of thesemiconductor wafers are polished on the turntable 509 one afteranother. Further, in the case where the number of semiconductor waferscounted from the uppermost position of the wafer cassette is even, sucheven numbers of the semiconductor wafers are polished on the turntable510 one after another. Next, the polishing processes will be describedbelow.

1. The load-unload stage 1 is angularly positionally adjusted, and thewafer cassette 540 turns its front face to the direction in which thetransfer robot 502 can transfer the semiconductor wafers to or from thewafer cassette 540.

2. The transfer robot 502 adjusts its angular position and heightposition, and the hand of the transfer robot 502 holds the semiconductorwafer in the wafer cassette 540 under vacuum, and takes out thesemiconductor wafer from the wafer cassette 540. In this case, in thetransfer robot 502, the hand for handling a clean semiconductor wafer isused.

3. The transfer robot 502 adjusts again its angular position and heightposition while the transfer robot 502 holds the semiconductor wafer, andtransfers the semiconductor wafer to the reversing device 504.

4. The reversing device 504 chucks the semiconductor wafer transferredfrom the transfer robot 502, and after it is confirmed that thesemiconductor wafer is normally chucked, the semiconductor wafer isrotated through 180° to make the surface thereof to be polished facingdownward.

5. After it is confirmed that the reversing device 504 is normallyrotated through 180°, the transfer robot 506 adjusts its angularposition and height position. Thereafter, the chuck of the reversingdevice 504 is opened and the hand of the transfer robot 506 receives thesemiconductor wafer from the reversing device 504. In this case, in thetransfer robot 506, the hand for handling a clean semiconductor wafer isused.

6. The transfer robot 506 adjusts again its angular position and heightposition and transfers the semiconductor wafer to the wafer station 520.After it is confirmed that the semiconductor wafer is transferred to thewafer station 520 normally, in the case where the load pusher 515 islocated in the first position and the semiconductor wafer is not placedon the load pusher 515, the shutter 518 is opened and the semiconductorwafer is transferred to the load pusher 515.

7. After it is confirmed that the semiconductor wafer is transferred tothe load pusher 515, the rotary transporter 519 is rotated to allow theload pusher 515 to move to a second position, i.e. a wafer transferposition to the top ring 512.

8. After it is confirmed that the load stage 515 moves to the wafertransfer position, the load pusher 515 is elevated to chuck the outerperiphery of the top ring 512. Thereafter, the stage on which thesemiconductor wafer is placed is further elevated, and the backsidesurface of the semiconductor wafer contacts the wafer holding surface ofthe top ring 512. At this time, a sock absorber using a spring providedat the lower part of the stage is operated to prevent the semiconductorwafer from being damaged. The load pusher 515 is elevated by apredetermined distance, and stopped. Then, the top ring 512 holds thesemiconductor wafer under vacuum.

9. After it is confirmed that the top ring 512 holds the semiconductorwafer normally under vacuum, the rotating shaft 533 for supporting thetop ring arm 511 is rotated, and top ring 512 moves to a polishingposition on the turntable 509.

10. After it is confirmed that the top ring 512 moves to the polishingposition, the turntable 509 which has been rotated at an idling speedand the top ring which has been stopped are rotated in the samedirection at predetermined speeds, and a polishing liquid is suppliedonto the turntable 509 from the polishing liquid supply nozzle 513 in apredetermined kind and amount. Thereafter, the top ring 512 is lowered,and after it is confirmed that the top ring 512 reaches the turntable509, the semiconductor wafer is pressed against the turntable 509 by thetop ring 512 under a predetermined pressure and polished for apredetermined time. The above predetermined speed, kind, amount,pressure, time, and the like are inputted in advance. After thispolishing process, a further polishing process may be carried out whiledifferent polishing liquid is supplied or liquid containing no solidmaterial is supplied.

11. After polishing of the semiconductor wafer is completed, the supplyof the polishing liquid from the polishing liquid supply nozzle 513 isstopped, and the top ring 512 holds the semiconductor wafer undervacuum. The shaft 533 for supporting the top ring arm 511 is rotated sothat the top ring 512 moves to a position where the top ring 512projects from the outer periphery of the turntable 509 by about half.Next, the top ring 512 is raised, and the top ring 512 is furtherrotated to the second position.

12. After it is confirmed that the top ring 512 is located above thesecond position, the unload pusher 516 is raised to chuck the top ring512 and the raising of the top ring 512 is stopped. At this time, thestage for placing the semiconductor wafer in the unload pusher 516 islocated so as to keep a certain gap between the stage and thesemiconductor wafer held by the top ring 512. Next, the top ring 512shuts off vacuum, blows air or nitrogen and pure water to remove thesemiconductor wafer therefrom and transfers the semiconductor wafer ontothe pusher 516.

13. After the semiconductor wafer is removed from the top ring 512, theunload pusher 516 is lowered.

14. The unload pusher 516 is lowered, and after it is confirmed that thesemiconductor wafer is placed on the unload pusher 516, the rotarytransporter 519 is rotated to move the unload pusher 516 to the firstposition. In this state, pure water is ejected from the rinsing nozzles542 to clean the top ring 512, and at the same time, a cleaning liquidis ejected from the rinsing nozzles 543 to clean the semiconductorwafer. At this time, a semiconductor wafer to be polished has beentransferred to the load pusher 515 by the transfer robot 508. Further,the load pusher 515 is located at the second position, and pure water isejected from the rinsing nozzle 544 to the semiconductor wafer forrinsing pure water which has fallen thereon. Therefore, a polishingprocess is carried out in the same manner as described above.

15. After rinsing of the top ring 512 and the semiconductor wafer iscompleted, the shutter 518 is opened and the transfer robot 508 adjustsits angular position and height position to receive the semiconductorwafer from the unload pusher 516. After it is confirmed that the loadpusher 515 transfers the semiconductor wafer to the top ring 512, therotary transporter 519 is rotated to move the unload pusher 516 to thesecond position.

16. After the transfer robot 508 receives the semiconductor wafer fromthe unload pusher 516, the transfer robot 508 adjusts its angularposition and height position to transfer the semiconductor wafer to thecleaning apparatus 507, and at the same time, the cleaning apparatus 507chucks the semiconductor wafer.

17. After it is confirmed that the cleaning apparatus 507 chucks thesemiconductor wafer normally, a primary cleaning of the polishedsemiconductor wafer is conducted to clean both surfaces of thesemiconductor wafer.

18. After the cleaning process of the cleaning apparatus 507 iscompleted, the transfer robot 506 adjusts its angular position andheight position and receives the semiconductor wafer by inserting thehand into the cleaning apparatus 507 through another opening. In thiscase, in the transfer robot 506, the hand for handling a dirtysemiconductor wafer is used.

19. The transfer robot 506 adjusts again its angular position and heightposition and transfers the semiconductor wafer to the reversing device505, and at the same time, the reversing device 505 chucks thesemiconductor wafer.

20. After it is confirmed that the reversing device 505 chucks thesemiconductor wafer normally, pure water is ejected from the rinsingnozzles attached to the reversing device 505 to prevent thesemiconductor wafer from being dried. At the same time, the reversingdevice 505 is rotated through 180° to make the polished surface of thesemiconductor wafer facing upward.

21. After it is confirmed that the reversing device 505 is rotatednormally through 180°, the transfer robot 502 adjusts its angularposition and height position to receive the semiconductor wafer from thereversing device 505 by the hand, and at the same time, the reversingdevice 505 opens the chuck mechanism. In this case, in the transferrobot 502, the hand for handling a dirty semiconductor wafer is used.

22. The transfer robot 502 adjusts its angular position and heightposition, and transfers the semiconductor wafer to the cleaningapparatus 503, and at the same time, the cleaning apparatus 503 chucksthe semiconductor wafer.

23. After it is confirmed that the cleaning apparatus 503 chucks thesemiconductor wafer normally, a secondary cleaning of the polishedsemiconductor wafer is conducted.

24. After cleaning of the semiconductor wafer by the cleaning apparatus503 is completed, the transfer robot 502 adjusts its angular positionand height position to receive the semiconductor wafer from the cleaningapparatus 503 by the hand. In this case, in the transfer robot 502, thehand for handling a clean semiconductor wafer is used.

25. The transfer robot 502 adjusts again its angular position and heightposition, and transfers the semiconductor wafer to the wafer cassette540 in which the polished semiconductor wafer is returned to itsoriginal position stored before polishing.

26. Even numbers of the semiconductor wafers counted from the uppermostposition of the wafer cassette after the second semiconductor wafer aretransferred to the turntable 510, polished, cleaned and returned to thewafer cassette one after another in the same manner as described above.In this case, the top ring 512 is moved in the direction opposite to thetop ring 512 for the turntable 509.

In the operations described in the steps 1 to 26 and described in thefirst embodiment, the odd numbers of semiconductor wafers are assignedto the turntable 509 and the even numbers of semiconductor wafers areassigned to the turntable 510. However, the software may be provided sothat the semiconductor wafers in one wafer cassette are assigned to theturntable 509, and the semiconductor wafers in another wafer cassetteare assigned to the turntable 510. Further, two or more wafer cassettesmay be assigned to each of the turntables, or the polishing apparatusmay have such a structure that the semiconductor wafers are processedone by one.

Although the pushers are provided on the rotary transporter in theembodiment shown in FIG. 66, the pushers may be provided below therotary transporter in the same manner as the embodiment shown in FIG.52. Further, the rotary transporter is not necessarily required to havethe shape of table, and the rotary transporter may have such a shapethat the load pusher and the unload pusher are fixed to a rotatingshaft.

FIGS. 67 through 82 are diagrams illustrative of operation of the rotarytransporter according to another embodiment. In FIGS. 67 through 82, thetransfer robots 506, 508 and 508 are represented by Robot No. 2, RobotNo. 3 and Robot No. 4, the load stages of the rotary transporter 519 arerepresented by LD stage for 1 and LD stage for 2, and the unload stagesof the rotary transporter 519 are represented by ULD stage for 1 and ULDstage for 2. Further, the top rings 512 are represented by TR1 and TR2.In the initial state shown in FIG. 67, the two load stages LD arelocated adjacent to the respective top rings TR1 and TR2, respectively,and two unload stages ULD are located adjacent to the respective RobotsNo. 3 and No. 4.

Each of stages ate arranged such that a load stage for the firstturntable, an unload stage for the first turntable, an unload stage forthe second turntable, and a load stage for the second turntable arelocated in a clockwise direction around a rotating shaft of said rotarytransporter.

Next, the operation of the rotary transporter will be described withreference to FIGS. 67 through 82.

In step 1, as shown in FIG. 67, the robot No. 2 holds the wafer 1 to bepolished at the first turntable (TT1).

In step 2, as shown in FIG. 68, the rotary transporter turns through anangle of 90° from the state shown in FIG. 67 in the clockwise direction.Then, the robot No. 2 transfers the wafer 1 to the LD stage for 1.

In step 3, as shown in FIG. 69, the rotary transporter turns back to thestate shown in FIG. 67.

In step 4, as shown in FIG. 70, the pusher is raised to receive thewafer 1 from the stage and transfers it to the TR1. Then, the TR1 startspolishing of the wafer 1. The robot No. 2 holds the wafer 2 to bepolished at the second turntable (TT2).

In step 5, as shown in FIG. 71, the rotary transporter turns through anangle of 90° from the state shown in FIG. 70 in the counterclockwisedirection. Then, the robot No. 2 transfers the wafer 2 to the LD stagefor 2.

In step 6, as shown in FIG. 72, the rotary transporter turns back to thestate shown in FIG. 70 (=FIG. 67). The robot No. 2 holds the wafer 3 tobe polished at the first turntable (TT1).

In step 7, as shown in FIG. 73, the pusher is raised to receive thewafer 2 from the stage and transfers it to the TR2. Then, the TR2 startspolishing of the wafer 2.

In step 8, as shown in FIG. 74, the rotary transporter turns through anangle of 90° from the state shown in FIG. 73 in the clockwise direction.Then, the robot No. 2 transfers the wafer 3 to the LD stage for 1.

In step 9, as shown in FIG. 75, the rotary transporter turns through anangle of 180° from the state shown in FIG. 74 in the counterclockwisedirection. The robot No. 2 holds the wafer 4 to be polished at thesecond turntable (TT2).

In step 10, as shown in FIG. 76, after polishing at the first turntable(TT1), the pusher is raised to receive the polished wafer 1 from the TR1and transfers it to the ULD stage for 1. The robot No. 2 transfers thewafer 4 to the LD stage for 2.

Instep 11, as shown in FIG. 77, the rotary transporter turns through anangle of 90° from the state shown in FIG. 76 in the clockwise direction.Then, the polished wafer 1 is cleaned by pure water (deionized water) inthis position. The robot No. 2 holds the wafer 5 to be polished at thefirst turntable (TT1).

In step 12, as shown in FIG. 78, the pusher is raised to receive thewafer 3 from the stage and transfers it to the TR1. Then, the TR1 startspolishing of the wafer 3. The robot No. 3 takes the polished wafer 1from the ULD stage for 1 after cleaning.

In step 13, as shown in FIG. 79, the rotary transporter turns through anangle of 90° from the state shown in FIG. 78 in the clockwise direction.Then the robot No. 2 transfers the wafer 5 to the LD stage for 1.

In step 14, as shown in FIG. 80, after polishing at the second turntable(TT2), the pusher is raised to receive the polished wafer 2 from the TR2and transfers it to the ULD stage for 2.

Instep 15, as shown in FIG. 81, the rotary transporter turns through anangle of 90° from the state shown in FIG. 80 in the counterclockwisedirection. Then, the polished wafer 2 is cleaned by pure water(deionized water) in this position. The robot No. 2 holds the wafer 6 tobe polished at the second turntable (TT2).

In step 16, as shown in FIG. 82, the pusher is raised to receive thewafer 4 from the LD stage for 2 and transfers it to the TR2. Then, theTR2 starts polishing of the wafer 4. The robot No. 4 takes the polishedwafer 2 from the ULD stage for 2 after cleaning.

A polishing apparatus according to a fourth embodiment of the presentinvention will be described below with reference to FIGS. 83 through 90.In the embodiment shown in FIGS. 83 through 90, elements (or components)having the same or similar functions as the elements (or components) inthe embodiment shown in FIGS. 1 through 48 will be described using thesame reference numerals.

FIG. 83 shows a layout of various components of a polishing apparatusaccording to the fourth embodiment of the present invention. FIG. 84shows the polishing apparatus shown in FIG. 83 in perspective. In FIGS.83 and 84, a housing which encloses an overall structure of thepolishing apparatus is not shown. Further, in FIG. 84, partition wallsare not shown.

In the polishing apparatus according to the first embodiment shown inFIGS. 1 through 48, a single common rotary transporter 27 having fourstages which are rotated is provided as a common transporter for twopolishing units disposed in the areas C and D. However, in the polishingapparatus according to the fourth embodiment, a linear transporterhaving at least two stages movable linearly in a reciprocating manner isprovided as a dedicated transporter for each of the polishing unitsdisposed in the areas C and D.

As shown in FIGS. 83 and 84, a polishing apparatus according to thepresent invention comprises four load-unload stages 2 each for placing awafer cassette 1 which accommodates a plurality of semiconductor wafers.The load-unload stage 2 may have a mechanism for raising and loweringthe wafer cassette 1. A transfer robot 4 having two hands is provided ona moving mechanism 3 so that the transfer robot 4 can move along themoving mechanism 3 and access the respective wafer cassettes 1 on therespective load-unload stages 2. The moving mechanism 3 comprises alinear motor.

By utilizing the linear motor, the transfer robot 4 can transport thesemiconductor wafer having a large diameter stably at a high speed. Inthe embodiment shown in FIG. 83, as the load-unload stage 2 for placingthe wafer cassette 1 thereon, SMIF (Standard Manufacturing InterfacePod) or FOUP (Front Opening Unified Pod) is used, and is externallyattached to the polishing apparatus. The SMIF and FOUP are an airtightcontainer in which a wafer cassette or wafer cassettes are housed andenclosed with outer walls for thereby keeping environment independent ofan outer space.

In the case where the SMIF or FOUP is provided in the load-unload stage2, by opening a shutter 52 provided on the housing 46 in the polishingapparatus and a shutter of the SMIF or the FOUP, the polishing apparatusand the wafer cassette side are integrated with each other. After thepolishing process is finished, the shutter of the SMIF or the FOUP isclosed, and the SMIF or the FOUP is separated from the polishingapparatus and automatically or manually transported to a next process.Therefore, it is necessary to keep internal atomosphere of the SMIP orthe FOUP clean.

Thus, downflow of clean air which has passed through a chemical filteris formed in the area A where the semiconductor wafer is moved beforethe semiconductor wafer is returned to the wafer cassette. Further,since the linear motor is used for moving the transfer robot 4,generation of dust is suppressed, and atmosphere in the area A can bekept clean. In order to keep semiconductor wafers in the wafer cassette1 clean, a chemical filter or a fan may be incorporated in an airtightcontainer such as the SMIF or the FOUP to maintain cleanliness of theatmosphere in the container. This container may be called clean box.

Two cleaning apparatuses 5 and 6 are disposed at the opposite side ofthe wafer cassettes 1 with respect to the moving mechanism 3 of thetransfer robot 4. The cleaning apparatuses 5 and 6 are disposed atpositions that can be accessed by the hands of the transfer robot 4.Between the two cleaning apparatuses 5 and 6 and at apposition that canbe accessed by the transfer robot 4, there is provided a wafer station50 having four wafer supports 7, 8, 9 and 10.

An area B in which the cleaning apparatuses 5 and 6 and the waferstation 50 having the wafer supports 7, 8, 9 and 10 are disposed and anarea A in which the wafer cassettes 1 and the transfer robot 4 aredisposed are partitioned by a partition wall 14 so that the cleanlinessof the area B and the area A can be separated. The partition wall 14 hasan opening for allowing semiconductor wafers to pass therethrough, and ashutter 11 is provided at the opening of the partition wall 14. Atransfer robot 20 is disposed at a position where the transfer robot 20can access the cleaning apparatus 5 and the three wafer supports 7, 9and 10, and a transfer robot 21 is disposed at a position where thetransfer robot 21 can access the cleaning apparatus 6 and the threewafer supports 8, 9 and 10.

A cleaning apparatus 22 is disposed at a position adjacent to thecleaning apparatus 5 and accessible by the hands of the transfer robot20, and another cleaning apparatus 23 is disposed at a position adjacentto the cleaning apparatus 6 and accessible by the hands of the transferrobot 21.

All the cleaning apparatuses 5, 6, 22 and 23, the wafer supports 7, 8, 9and 10 of the wafer station 50, and the transfer robots 20 and 21 areplaced in the area B. The pressure in the area B is adjusted so as to belower than the pressure in the area A. Each of the cleaning apparatuses22 and 23 is capable of cleaning both surfaces of a semiconductor wafer.

The polishing apparatus has a housing (not shown) for enclosing variouscomponents therein. The housing constitutes an enclosing structure. Theinterior of the housing is partitioned into a plurality of compartmentsor chambers (including the areas A and B) by partitions 14, 24A and 24B.

Two areas C and D constituting polishing chambers separated from thearea B are formed by partition walls 24A and 24B. In each of the twoareas C and D, there are provided two turntables, and a top ring forholding a semiconductor wafer and pressing the semiconductor waferagainst the turntables. That is, the turntables 34 and 36 are providedin the area C, and the turntables 35 and 37 are provided in the area D.Further, the top ring 32 is provided in the area C and the top ring 33is provided in the area D. An abrasive liquid nozzle 40 for supplying anabrasive liquid to the turntable 34 in the area C and a dresser 38 fordressing the turntable 34 are disposed in the area C. An abrasive liquidnozzle 41 for supplying an abrasive liquid to the turntable 35 in thearea D and a dresser 39 for dressing the turntable 35 a redisposed inthe area D. A dresser 48 for dressing the turntable 36 in the area C isdisposed in the area C, and a dresser 49 for dressing the turntable 37in the area D is disposed in the area D.

The turntables 34 and 35 are provided with respective atomizers 44 and45, in addition to the mechanical dressers 38, 39. The atomizer has sucha structure that a mixture of liquid such as pure water and gas such asnitrogen is atomized and the atomized fluid is ejected from a pluralityof nozzles toward the polishing surface. The main purpose of theatomizer is to wash away ground-off particles and the abrasive particlesattached to or deposited on the polishing surface.

By cleaning action of the polishing surface with fluid pressure of theatomizer 44 or 45 as well as dressing action of the mechanical dresser38 or 39, more desirable dressing of the polishing surface, i.e.,regeneration of the polishing surface can be achieved.

FIG. 85 shows the relationship between the top ring 32 and theturntables 34 and 36. The relationship between the top ring 33 and theturntables 35 and 37 is the same as that of the top ring 32 and theturntables 34 and 36. As shown in FIG. 85, the top ring 32 is supportedfrom a top ring head 31 by a top ring drive shaft 91 which is rotatable.The top ring head 31 is supported by a support shaft 92 which can beangularly positioned, and the top ring 32 can access the turntables 34and 36. The dresser 38 is supported from a dresser head 94 by a dresserdrive shaft 93 which is rotatable. The dresser head 94 is supported byan angularly positionable support shaft 95 for moving the dresser 38between a standby position and a dressing position over the turntable34. A dresser head (swing arm) 97 is supported by an angularlypositionable support shaft 98 for moving a dresser 48 between a standbyposition and a dressing position over the turntable 36. The dresser 48has a retangular body longer than the diameter of the turntable 36. Thedresser head 97 for supporting the dresser 48 is swingable about thesupport shaft 98. A dresser fixing mechanism 596 is provided at the freeend of the dresser head 97 to support the dresser 48. The dresser fixingmechanism 596 and the dresser 48 make a pivot motion to cause thedresser 48 to move like a wiper for wiping a windowshield of a car onthe turntable 36 without rotating the dresser 48 about its own axis. Theturntables 36, 37 comprise the scroll-type table described above.

As shown in FIG. 83, in the area C separated from the area B by thepartition wall 24A and at a position that can be accessed by the handsof the transfer robot 20, there is provided a reversing device 28 forreversing a semiconductor wafer. In the area D separated from the area Bby the partition wall 24B and at a position that can be accessed by thehands of the transfer robot 21, there is provided a reversing device 28′for reversing a semiconductor wafer. The partition walls 24A, 24Bbetween the area B and the areas C, D have respective openings each forallowing semiconductor wafers to pass therethrough, one of which is usedfor transferring the semiconductor wafer to or from the reversing device28 and the other of which is used for transferring the semiconductorwafer to or from the reversing device 28′. Shutters 25 and 26 areprovided at the respective openings of the partition walls 24A and 24B.

The reversing devices 28 and 28′ have a chuck mechanism for chucking asemiconductor wafer, a reversing mechanism for reversing a semiconductorwafer, and a semiconductor wafer detecting sensor for detecting whetherthe chuck mechanism chucks a semiconductor wafer or not, respectively.The transfer robot 20 transfers a semiconductor wafer to the reversingdevice 28, and the transfer robot 21 transfers a semiconductor wafer tothe reversing device 28′.

In the area C constituting one of the polishing chambers, there isprovided a linear transporter 27A for transporting the semiconductorwafer between the reversing device 28 and the top ring 32. In the area Dconstituting the other of the polishing chambers, there is provided alinear transporter 27B for transporting the semiconductor wafer betweenthe reversing device 28′ and the top ring 33.

On the right side of FIG. 85, the relationship between the lineartransporter 27A, and the liter 29 and the pusher 30 is shown. Therelationship between the linear transporter 27B, and the lifter 29′ andthe pusher 30′ is the same as that shown in FIG. 85. In the followingdescription, the top ring 32, the reversing device 28, the lifter 29 andthe pusher 30 are used for explanation of their structure and theirtransfer operation.

As shown in FIG. 85, the lifter 29 and the pusher 30 are disposed belowthe linear transporter 27A, and the reversing device 28 is disposedabove the linear transporter 27A. The top ring 32 is angularly movableso as to be positioned above the pusher 30 and the linear transporter27A.

FIG. 86 shows the linear transporter 27A, the lifter 29 and the pusher30 in perspective. As shown in FIG. 86, the linear transporter 27Acomprises two stages 901, 902 linearly movable in a reciprocatingfashion for placing the semiconductor wafer thereon, respectively,support members 903, 904 for supporting the stages 901, 902,respectively, and air cylinders 906, 905 with a guide for moving thesupport members 903, 904 linearly in a reciprocating fashion,respectively. The air cylinders 906, 905 are fixed symmetrically toupper and lower surfaces of a support plate 921 (see FIGS. 88B and 88C).The two stages 901 and 902 are positioned at different heights so thatthey are movable freely along the same route without mutual physicalinterference. Therefore, the stage 901 can be positioned above thelifter 29 and the stage 902 can be positioned above the pusher 30, andafter the stages 901, 902 are simultaneously moved and pass each other,the stage 901 can be positioned above the pusher 30 and the stage 902can be positioned above the lifter 29. The stages 901, 902 have fourpins 920, respectively which support a ring-shaped wafer tray 925.

FIGS. 87A and 87B show the air cylinder 905 (or 906) with a guide, andFIG. 87A is a perspective view showing the air cylinder 905 and FIG. 87Bis a plan view with partially cross-section showing an essential part ofFIG. 87A. As shown in FIGS. 87A and 87B, the air cylinder 905 with aguide comprises a slider 908 linearly movable in a reciprocating fashionfor supporting and moving the support member 903, a guide rail 909 forguiding the slider 908, and a magnet-type cylinder 910 coupled to theslider 908 for moving the slider 908 linearly in a reciprocatingfashion. The magnet-type cylinder 910 comprises a guide pipe 911, apiston 912 linearly movable in the guide pipe 911 by supplying air tothe interior of the guide pipe 911, and a movable member 914 which ismovable together with the piston 912 by magnetic coupling of magnets 913which are provided in the piston 912 and the movable member 914.Therefore, when air is supplied to the interior of the guide pipe 911,the piston 912 is moved in the guide pipe 911, and the movable member914 which is magnetically coupled to the piston 912 is moved togetherwith the piston 912. Thus, the slider 908 is moved along the guide rail909, and the support member 903 and the stage 901 which are fixed to theslider 908 are linearly moved in a reciprocating fashion.

FIGS. 88A, 88B and 88C show the entire structure of the lineartransporter 27A, and FIG. 88A is a plan view, FIG. 88B is a view asviewed from an arrow A of FIG. 88A, and FIG. 88C is a view as viewedfrom an arrow B of FIG. 88A. In FIG. 88A, the wafer tray 925 is notshown.

As shown in FIGS. 88B and 88C, the stages 901 and 902 are positioned atdifferent heights so that they are movable freely without mutualphysical interference. The wafer tray 925 is placed on the pins 920provided on each of the stages 901 and 902. The wafer tray 925 isautomatically centered by engagement between the pins 920 and the outerperiphery of the wafer tray 925. The wafer tray 925 has an upper holdingsurface 926 for supporting the semiconductor wafer. The upper holdingsurface 926 is arranged so as to allow its contact surface with thesemiconductor wafer to be minimized. As shown in FIG. 89, the waferholding surface 926 is uneven in its entirety. The projecting portions926 a have their tapered surfaces so as to have a higher peripheralportion, thus reducing the contact areas with the semiconductor wafer.In this embodiment, the stage 901 serves as a loading stage for loadingthe semiconductor wafer on the top ring 32, and the stage 902 serves asan unloading stage for unloading the semiconductor wafer from the topring 32.

FIG. 90 is a schematic view showing transfer operation of asemiconductor wafer between the reversing device and the lineartransporter, and between the linear transporter and the top ring.

The semiconductor wafer 101, to be polished, which has been transportedto the reversing device 28 is reversed by the reversing device 28. Whenthe lifter 29 is raised, the wafer tray 925 on the stage 901 for loadingin the linear transporter 27A is transferred to the lifter 29. Thelifter 29 is further raised, and the semiconductor wafer 101 istransferred from the reversing device 28 to the wafer tray 925 on thelifter 29. Then, the lifter 29 is lowered, and the semiconductor wafer101 is transferred together with the wafer tray 925 to the stage 901 forloading in the linear transporter 27A. The semiconductor wafer 101 andthe wafer tray 925 placed on the stage 901 are transported to a positionabove the pusher 30 by linear movement of the stage 901.

At this time, the stage 902 for unloading in the linear transporter 27Areceives a polished semiconductor wafer 101 from the top ring 32, andthen is moved toward a position above the lifter 29. The stage 901 forloading and the stage 902 for unloading pass each other. When the stage901 reaches a position above the pusher 30, the top ring 32 ispositioned at the location shown in FIG. 90 beforehand by a swing motionthereof.

Next, the pusher 30 is raised, and receives the wafer tray 925 and thesemiconductor wafer 101 from the stage 901. Then, the pusher 30 isfurther raised, and only the semiconductor wafer 101 is transferred tothe top ring 32.

The semiconductor wafer 101 transferred to the top ring 32 is held undervacuum by a vacuum attraction mechanism of the top ring 32, andtransported to the turntable 34. Thereafter, the semiconductor wafer ispolished by a polishing surface comprising a polishing cloth or agrinding stone (or a fixed abrasive plate) attached on the turntable 34.The second turntable 36 is disposed at a position that can be accessedby the top ring 32. With this arrangement, a primary polishing of thesemiconductor wafer can be conducted by the first turntable 34, and thena secondary polishing of the semiconductor wafer can be conducted by thesecond turntable 36. Alternatively, the primary polishing of thesemiconductor wafer can be conducted by the second turntable 36, andthen the secondary polishing of the semiconductor wafer can be conductedby the first turntable 34.

The semiconductor wafer 101 which has been polished is returned to thereversing device 28 in the reverse route to the above (described later).The semiconductor wafer returned to the reversing device 28 is rinsed bypure water or chemicals supplied from rinsing nozzles. Further, thewafer holding surface of the top ring 32 from which the semiconductorwafer has been removed is also cleaned by pure water or chemicalssupplied from cleaning nozzles.

Next, processes conducted in the polishing apparatus shown in FIGS. 83through 85 will be described below.

In two cassette parallel processing in which two-stage cleaning isperformed, one semiconductor wafer is processed in the following route:the wafer cassette CS1→the transfer robot 4→the wafer support 7 of thewafer station→50 the transfer robot 20→the reversing device 28→the stage901 for loading in the linear transporter 27A→the top ring 32→theturntable 34→the turntable 36 (as necessary)→the stage 902 for unloadingin the linear transporter 27A→the reversing device 28→the transfer robot20→the cleaning apparatus 22→the transfer robot 20→the cleaningapparatus 5→the transfer robot 4→the wafer cassette CS1.

The other semiconductor wafer is processed in the following route: thewafer cassette CS2→the transfer robot 4→the wafer support 8 of the waferstation 50→the transfer robot 21→the reversing device 28′→the stage 901for loading in the linear transporter 27B→the top ring 33→the turntable35→the turntable 37 (as necessary)→the stage 902 for unloading in thelinear transporter 27B→the reversing device 28′→the transfer robot21→the cleaning apparatus 23→the transfer robot 21→the cleaningapparatus 6→the transfer robot 4→the wafer cassette CS2.

In two cassette parallel processing in which three-stage cleaning isperformed, one semiconductor wafer is processed in the following route:the wafer cassette CS1→the transfer robot 4→the wafer support 7 of thewafer station 50→the transfer robot 20→the reversing device 28→the stage901 for loading in the linear transporter 27A→the top ring 32→theturntable 34→the turntable 36 (as necessary)→the stage 902 for unloadingin the linear transporter 27A→the reversing device 28→the transfer robot20→the cleaning apparatus 22→the transfer robot 20→the wafer support 10of the wafer station 50→the transfer robot 21→the cleaning apparatus6→the transfer robot 21→the wafer support 9 of the wafer station 50→thetransfer robot 20→the cleaning apparatus 5→the transfer robot 4→thewafer cassette CS1.

The other semiconductor wafer is processed in the following route: thewafer cassette CS2→the transfer robot 4→the wafer support 8 of the waferstation 50→the transfer robot 21→the reversing device 28′→the stage 901for loading in the linear transporter 27B→the top ring 33→the turntable35→the turntable 37 (as necessary)→the stage 902 for unloading in thelinear transporter 27B→the reversing device 28′→the transfer robot21→the cleaning apparatus 23→the transfer robot 21→the cleaningapparatus 6→the transfer robot 21→the wafer support 9 of the waferstation 50→the transfer robot 20→the cleaning apparatus 5→the transferrobot 4→the wafer cassette CS2.

In serial processing in which three-stage cleaning is performed, thesemiconductor wafer is processed in the following route: the wafercassette CS1→the transfer robot 4→the wafer support 7 of the waferstation 50→the transfer robot 20→the reversing device 28→the stage 901for loading in the linear transporter 27A→the top ring 32→the turntable34→the turntable 36 (as necessary)→the stage 902 for unloading in thelinear transporter 27A→the reversing device 28→the transfer robot 20→thecleaning apparatus 22→the transfer robot 20→the wafer support 10 of thewafer station 50→the transfer robot 21→the reversing device 28′→thestage 901 for loading in the linear transporter 27B→the top ring 33→theturntable 35→the turntable 37 (as necessary)→the stage 902 for unloadingin the linear transporter 27B→the reversing device 28′→the transferrobot 21→the cleaning apparatus 23→the transfer robot 21→the cleaningapparatus 6→the transfer robot 21→the wafer support 9 of the waferstation 50→the transfer robot 20→the cleaning apparatus 5→the transferrobot 4→the wafer cassette CS1.

In the above examples, it is described that one semiconductor wafer istaken out from the wafer cassette CS1, and another semiconductor waferis taken out from the wafer cassette CS2. However, the wafer cassettesCS1 and CS2 may be used for dedicatedly supplying the semiconductorwafers to the turntable 34, and the wafer cassettes CS3 and CS4 may beused for dedicatedly supplying the semiconductor wafers to the turntable35.

Next, the operation of the linear transporter 27A, the lifter 29 and thepusher 30 will be described. The operation of the linear transporter27B, the lifter 29′ and the pusher 30′ is the same as that of the lineartransporter 27A, the lifter 29 and the pusher 30, and will not bedescribed. Further, the reversing device 28, the lifter 29 and thepusher 30 have substantially the same structure as those in the firstembodiment, and the detailed structure of them will not be describedbelow. However, the pusher 30 in the fourth embodiment has a push stage143′ slightly different from the push stage 143 in the first embodiment.

Transferring a Semiconductor Wafer

The stage 901 for loading in the linear transporter 27A is located abovethe lifter 29. The semiconductor wafer 101 to be polished is transferredfrom the transfer robot 20 to the reversing device 28 (see FIGS. 29A and29B). Thereafter, the semiconductor wafer 101 is reversed by thereversing device 28 to cause a pattern surface (the surface on whichsemiconductor device is formed) of the semiconductor wafer to facedownward. The lifter 29 (see FIG. 30) is raised, and the stage 260 ofthe lifter 29 is engaged with the wafer tray 925 on the stage 901 of thelinear transporter 27A.

Next, the lifter 29 is raised to a position where the wafer tray 925receives the semiconductor wafer 101 from the reversing device 28 whilethe lifter 29 supports the wafer tray 925 thereon, and the lifter 29 isstopped thereat.

When the sensor 266 provided on the air cylinder 261 detects the stop ofthe lifter 29 at a position where the stage 260 is located immediatelybelow the semiconductor wafer 101, the reversing device 28 releases thesemiconductor wafer 101 by opening the arms and the semiconductor wafer101 is placed on the wafer tray 925 on the stage 260 of the lifter 29.Thereafter, the lifter 29 is lowered while the lifter 29 holds the wafertray 925 having the semiconductor wafer 101 thereon.

The wafer tray 925 holding the semiconductor wafer 101 and placed on thelifter 29 is centered by the pins 920 on the stage 901 of the lineartransporter 27A, and transferred from the lifter 29 to the stage 901 ofthe linear transporter 27A and placed on the stage 901. After the wafertray 925 is placed on the stage 901 of the linear transporter 27A, thelifter 29 continues to be operated to cause the stage 260 to be lowereduntil the stage 260 does not interfere with the linear transporter 27Aeven when the stage 901 is moved.

Loading a Semiconductor Wafer

When lowering of the lifter 29 is completed, the stage 901 of the lineartransporter 27A is moved, and the wafer tray 925, having thesemiconductor wafer 101 thereon, on the stage 901 of the lineartransporter 27A is positioned above the pusher 30 (see FIG. 33). Afterpositioning of the stage 901 of the linear transporter 27A is completed,the pusher 30 is raised together with the components associated with theguide stage 141 by the air cylinder 146. While the pusher 30 is raised,the guide stage 141 passes through the wafer holding position of thestage 901 of the linear transporter 27A. At this time, the wafer tray925 holding the semiconductor wafer 101 is engaged by the push stage143′ of the pusher 30, and transferred from the stage 901 of the lineartransporter 27A to the pusher 30.

While the push stage 143′ holds the wafer tray 925, the top ring guides148 are raised without being stopped, and the guide ring 301 of the topring 32 is guided by the tapered surfaces 208 of the top ring guides148. The center of the top ring guides 148 is aligned with the center ofthe top ring 32 by the linear way 149 movable in X and Y directions, andthe upper surface 200 of the top ring guides 148 contact the lowersurface of the guide ring 301 and lifting of the guide stage 141 iscompleted.

When the upper surface 200 of the top ring guides 148 contact the lowersurface of the guide ring 301, the guide stage 141 is fixed and is notraised anymore. However, the air cylinder 146 continues to be actuateduntil the stopper fixed to the rod of the air cylinder 146 contacts theshock absorber 156, and hence only the spline shaft 142 continues to beraised because the compression spring 152 is compressed, and the pushstage 143′ is further raised. After the semiconductor wafer 101 contactsthe top ring 32, the lifting stroke of the air cylinder 146 is absorbedby the compression springs 159 to thereby protect the semiconductorwafer 101 against damage.

Next, the push stage 143′ is further raised by the air cylinder 145while the push stage 143′ holds the wafer tray 925, and thesemiconductor wafer 101 is held by the top ring 32 under vacuum by thevacuum attraction mechanism of the top ring 32. Thereafter, the wafertray 925 is lowered together with the push stage 143′ by the aircylinder 145 which is actuated in the opposite direction to the aboveactuation.

The pusher 30 is lowered together with the components associated withthe guide stage 141 by the air cylinder 146, and the wafer tray 925 istransferred to the stage 901 of the linear transporter 27A while thepusher 30 is lowered. The pusher 30 is further lowered, and then stoppedat a predetermined position.

Unloading a Semiconductor Wafer

The semiconductor wafer 101 which has been polished is transported bythe top ring 32 to a wafer unload position located above the pusher 30.By the movement of the stage 902 for unloading in the linear transporter27A, the wafer tray 925 on the stage 902 of the linear transporter 27Ais located above the pusher 30. Then, the pusher 30 is raised togetherwith the components associated with the guide stage 141 by the aircylinder 146. While the pusher 30 is raised, the guide stage 141 passesthrough the wafer holding position of the stage 902 of the lineartransporter 27A. At this time, the wafer tray 925 having nosemiconductor wafer is engaged by the push stage 143′ of the pusher 30,and transferred from the stage 902 of the linear transporter 27A to thepusher 30.

The guide ring 301 of the top ring 32 is guided by the tapered surfaces208 of the top ring guides 148. The center of the top ring guides 148 isaligned with the center of the top ring 32 by the linear way 149, andthe upper surface 200 of the top ring guides 148 contact the lowersurface of the guide ring 301 and the lifting of the guide stage 141 iscompleted.

At this time, the air cylinder 146 continues to be actuated until thestopper fixed to the rod of the air cylinder 146 contacts the shockabsorber 156. However, since the upper surface 200 of the top ringguides 148 contacts the lower surface of the guide ring 301 to cause theguide stage 141 to be fixed at this position, the air cylinder 146pushes the spline shaft 142 together with the air cylinder 145 againsturging force of the compression spring 152, thus lifting the push stage143′. In this embodiment, the air cylinder 146 is arranged to be furtheractuated after the top ring guides 148 contact the guide ring 301. Theshock generated at this time is absorbed by the spring 152.

After the lifting actuation of the air cylinder 146 is completed, thesemiconductor wafer 101 is removed from the top ring 32, and held by thewafer tray 925 for unloading.

After the semiconductor wafer 101 is held by the wafer tray 925, thepusher 30 starts to be lowered. Then, the wafer tray 925 is transferredtogether with the polished semiconductor wafer 101 to the stage 902 forunloading in the linear transporter 27A, and the pusher 30 continues tobe lowered and the operation of the pusher 30 is finished by completionof its lowering.

The stage 902 for unloading in the linear transporter 27A is moved, andthe wafer tray 925 holding the polished semiconductor wafer 101 thereonis located above the lifter 29. Then, the lifter 29 is raised, andreceives the wafer tray 925 holding the polished semiconductor wafer 101from the stage 902 of the linear transporter 27A. The lifter 29 isfurther raised to thus locate the semiconductor wafer at a wafertransfer position where the semiconductor wafer is transferred to thereversing device 28.

After the arms of the reversing device 28 hold the semiconductor wafer101, the lifter 29 is lowered to transfer the wafer tray 925 to thestage 902 for unloading in the linear transporter 27A. When the loweringof the lifter 29 is completed, the transfer operation of thesemiconductor wafer from the top ring 32 to the reversing device 28 iscompleted. Thereafter, the semiconductor wafer 101 is reversed by thereversing device 28, and then received by the transfer robot 20.

According to the polishing apparatus of the fourth embodiment, since alinear transporter having at least two stages which are linearly movedin a reciprocating fashion is provided as a dedicated transporter foreach of the polishing units, it is possible to shorten the time requiredto transfer a workpiece to be polished or a polished workpiece, such asa semiconductor wafer, between the reversing device and the top ring,for thereby greatly increasing the number of processed workpieces perunit time, i.e., throughput.

Further, when the workpiece is transferred between the stage of thelinear transporter and the reversing device, the workpiece istransferred between the wafer tray and the reversing device, and whenthe workpiece is transferred between the stage of the linear transporterand the top ring, the workpiece is transferred between the wafer trayand the top ring. Therefore, the wafer tray can absorb an impact or ashock on the workpiece generated when transferring, and hence thetransfer speed of the workpiece can be increased for thereby increasingthroughput.

Furthermore, the transfer of the semiconductor wafer from the reversingdevice to the top ring can be performed by the wafer tray removably heldby the respective stages of the linear transporter. Thus, for example,the transfer of the semiconductor wafer between the lifter and thelinear transporter or between the linear transporter and the pusher maybe eliminated to prevent dust from being generated and prevent thesemiconductor wafer from being damaged due to transfer error or clampingerror.

In the above-described embodiment, a plurality of wafer trays areassigned to loading wafer tray for holding a semiconductor wafer to bepolished and unloading wafer tray for holding a semiconductor waferwhich has been polished. Therefore, the semiconductor wafer to bepolished is transferred not from the pusher but from the loading wafertray to the top ring, and the polished semiconductor wafer istransferred from the top ring not to the pusher but to the unloadingwafer tray. Thus, the loading of the semiconductor wafer to the topring, and the unloading of the semiconductor wafer from the top ring areconducted by respective jigs (or components), i.e. the wafer tray, andhence the abrasive liquid or the like attached to the polishedsemiconductor wafer is prevented from being attached to a common supportmember for performing loading and unloading the semiconductor wafer. Asa result, the solidified abrasive liquid or the like is not attached tothe semiconductor wafer to be polished, and does not cause damage to thesemiconductor wafer to be polished.

In the above embodiment, the wafer tray for loading the semiconductorwafer and the wafer tray for unloading the semiconductor wafer areseparately used. However, a single wafer tray may be used for loadingand unloading the semiconductor wafer.

As described above, according to the present invention, it is possibleto shorten the time required to transfer a workpiece to be polished,such as a semiconductor wafer, to the top ring, for thereby greatlyincreasing the number of processed workpieces per unit time, i.e.,throughput.

Further, in the conventional polishing apparatus, the number of toprings is increased and the workpieces are simultaneously polished forthereby increasing throughput. Thus, the workpieces cannot be uniformlypolished due to the difference of individual top rings caused byincreasing of the top rings. In contrast thereto, in the presentinvention, by increasing the transfer speed of the workpieces,throughput can be increased by a reduced number of top rings.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1. A polishing apparatus comprising: at least three load-unload stageseach for placing a wafer cassette which accommodates a plurality ofwafers; a robot which moves along said at least three load-unloadstages, for accessing said respective wafer cassettes; a polishing unitfor polishing a plurality of wafers simultaneously; a cleaning anddrying unit for cleaning and drying a polished wafer; and a dummy waferstation for holding at least one dummy wafer or at least one qualitycontrol wafer.
 2. A polishing apparatus according to claim 1, whereinsaid robot is movable along a rail disposed in said polishing apparatus.3. A polishing apparatus according to claim 1, wherein said polishingunit comprises a plurality of top rings each for holding a respectivewafer during polishing operation.
 4. A polishing apparatus according toclaim 3, wherein said polishing unit comprises a plurality of polishingtables each for providing a polishing surface for the wafer.
 5. Apolishing apparatus according to claim 1, further comprising anotherrobot for transferring the wafer in a space between said load-unloadstages and said polishing unit.
 6. A polishing apparatus according toclaim 1, wherein said cleaning and drying unit comprises at least threecleaning apparatuses for cleaning the wafer.
 7. A polishing apparatusaccording to claim 1, wherein said load-unload stages, said robot, saidcleaning and drying unit, and said polishing unit are disposed in orderfrom one side of the polishing apparatus.
 8. A polishing apparatusaccording to claim 1, wherein a partition is provided between saidpolishing unit and said cleaning and drying unit.
 9. A polishingapparatus according to claim 1, wherein a partition is provided betweensaid load-unload stages and said cleaning and drying unit.
 10. Apolishing apparatus according to claim 1, wherein said dummy waferstation holds said at least one dummy wafer, and said at least one dummywafer is a substrate for use in stabilizing a polishing cloth in saidpolishing unit before a product wafer is processed.
 11. A polishingapparatus according to claim 1, wherein said dummy wafer station holdssaid at least one quality control wafer, and said at least one qualitycontrol wafer is a substrate for confirming the status or condition ofsaid polishing apparatus.
 12. A polishing apparatus of claim 1, whereinsaid dummy wafer station comprises a substrate detection sensor forconfirming the presence of a substrate in said dummy wafer station. 13.A polishing apparatus of claim 1, wherein said dummy wafer station isdisposed below said load-unload stages.
 14. A polishing apparatuscomprising: at least three load-unload stages each for placing a wafercassette which accommodates a plurality of wafers; a robot which movesalong said at least three load-unload stages, for accessing saidrespective wafer cassettes; a polishing unit for polishing a pluralityof wafers simultaneously; a cleaning and drying unit for cleaning anddrying a polished wafer; and a transporter for handling a plurality ofthe wafers at one time, and for moving a wafer to a preferable positionbelow a top ring which holds the wafer during polishing operation;wherein said robot and said cleaning and drying unit are disposedbetween said load-unload stages and said polishing unit.
 15. A polishingapparatus according to claim 14, wherein said transporter transfers thewafers to a plurality of the top rings.
 16. A polishing apparatusaccording to claim 14, further comprising a pusher disposed below saidtransporter for elevating the wafer on said transporter to the top ring.17. A polishing apparatus comprising: at least three load-unload stageseach for placing a wafer cassette which accommodates a plurality ofwafers; a robot which moves along said at least three load-unload statesfor accessing said respective wafer cassettes; a polishing unit forpolishing a plurality of wafers simultaneously; a cleaning and dryingunit for cleaning and drying a polished wafer; and a partition providedbetween said load-unload stales and said cleaning and drying unit,wherein said robot and said cleaning and drying unit are disposedbetween said load-unload stages and said polishing unit, and wherein apressure of a space in which said cleaning and drying unit is disposedis adjusted so as to be lower than a pressure of a space in which saidload-unload stages are disposed.
 18. A polishing apparatus according toclaim 17, wherein a pressure of a space in which said polishing unit isdisposed is adjusted so as to be lower than a pressure of the space inwhich said cleaning and drying unit is disposed.